Treatment algorithm

Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups: see disclaimer

ONGOING

constipation-predominant

1st line – lifestyle and dietary modifications

Back
ONGOING
|
constipation-predominant
|
pain or bloating not predominant
1st line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​​

Probiotics may also be considered. Probiotics can help reduce flatulence and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Consider – laxative

Back
ONGOING
|
constipation-predominant
|
pain or bloating not predominant
Consider – 

laxative

Additional treatment recommended for SOME patients in selected patient group

The American Gastroenterological Association suggests that polyethylene glycol (PEG) may be used for specific symptom relief, or as adjunctive therapy for the treatment of IBS with constipation (IBS-C).[78] American College of Gastroenterology guidelines contradict this, however, citing a lack of evidence that PEG alleviates abdominal pain, and thus global symptoms, in patients with IBS-C.[39] They therefore recommend against the use of PEG alone for the treatment of global IBS-C symptoms, although they recognise that clinicians may use PEG as first-line treatment of constipation in IBS, given its low cost and availability.[39]

2nd line – lifestyle and dietary modifications

Back
ONGOING
|
constipation-predominant
|
pain or bloating not predominant
2nd line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.​[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce flatulence and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Plus – secretagogue

Back
ONGOING
|
constipation-predominant
|
pain or bloating not predominant
Plus – 

secretagogue

Treatment recommended for ALL patients in selected patient group

Lubiprostone, linaclotide, plecanatide, or tenapanor are secretagogues that are recommended for patients with persistent constipation despite treatment with initial laxatives.[39]​​[53][78]

One systematic review and network meta-analysis examining the relative efficacy of these secretagogues across 18 randomised controlled trials found that they were all superior to placebo.[79] Linaclotide was the most efficacious agent for relieving constipation; plecanatide had the best safety profile.[79] Analyses utilised data extracted at a 12-week timepoint; longer-term effects are unknown.

Linaclotide and plecanatide are minimally absorbed 14-amino acid peptides that bind and activate the guanylate cyclase C receptor on the luminal surface of the enterocyte. This results in increased levels of cyclic guanosine monophosphate (cGMP), a second messenger that increases secretion of intestinal fluid.[80] Plecanatide and linaclotide are comparably effective, safe, and well tolerated.[39][81] Diarrhoea is a common side effect of both these medications.[53]

Treatment with lubiprostone, a chloride-channel 2 (CIC2) activator, is an alternative in patients with constipation-predominant IBS who do not tolerate laxatives or stool softeners, or in whom these are ineffective.[39][82][83]​ Lubiprostone is approved by the US Food and Drug Administration (FDA) for the treatment of IBS with constipation only in women aged ≥18 years. Diarrhoea is a less common adverse effect with lubiprostone than with other secretagogues; however, patients should be warned that nausea is a frequent side effect.[53]

Tenapanor, an inhibitor of the sodium-proton exchanger NHE3, is another alternative. It is effective for constipation and other global symptoms of IBS like bloating. As with linaclotide and plecanatide, diarrhoea is a side effect.[53]

Primary options

lubiprostone: women: 8 micrograms orally twice daily

OR

linaclotide: 290 micrograms orally once daily

OR

plecanatide: 3 mg orally once daily

OR

tenapanor: 50 mg orally twice daily

3rd line – lifestyle and dietary modifications

Back
ONGOING
|
constipation-predominant
|
pain or bloating not predominant
3rd line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce flatulence and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

1st line – lifestyle and dietary modifications

Back
ONGOING
|
constipation-predominant
|
with pain or bloating predominant
1st line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce abdominal bloating and flatulence, alleviate pain, and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Consider – laxative

Back
ONGOING
|
constipation-predominant
|
with pain or bloating predominant
Consider – 

laxative

Additional treatment recommended for SOME patients in selected patient group

The American Gastroenterological Association suggests that polyethylene glycol (PEG) may be used for specific symptom relief, or as adjunctive therapy for the treatment of symptoms of IBS with constipation (IBS-C).[78] American College of Gastroenterology (ACG) guidelines contradict this, however, citing a lack of evidence that PEG alleviates abdominal pain, and thus global symptoms, in patients with IBS-C.[39] They therefore recommend against the use of PEG alone for the treatment of global IBS-C symptoms, although they recognise that clinicians may use PEG as first-line treatment of constipation in IBS, given its low cost and availability.[39]

Plus – antispasmodic

Back
ONGOING
|
constipation-predominant
|
with pain or bloating predominant
Plus – 

antispasmodic

Treatment recommended for ALL patients in selected patient group

Antispasmodics may be considered for patients experiencing pain or bloating.[34][87] They act by relaxing smooth muscle, thereby reducing gut motility. One Cochrane review found that patients taking antispasmodics experienced significantly greater improvement in both abdominal pain and global IBS symptoms.[76] The effect of individual antispasmodics was difficult to interpret, however, because of the inclusion of 12 different drugs and the small number of studies evaluated for each drug. There was also considerable variation between the studies concerning diagnostic and inclusion criteria, dosing schedule, and study end points.[87]

Because of the lack of high-quality evidence available, American College of Gastroenterology (ACG) guidelines recommend against the use of antispasmodics currently available in the US to treat global IBS symptoms (dicyclomine and hyoscyamine). They concede that there are more robust data supporting the use of alternative antispasmodics available internationally.[39] The American Gastroenterological Association (AGA) differs in its guidance and does recommend hyoscyamine and dicyclomine.​[78][87]

Not all antispasmodic agents are universally available; for example, the non-anticholinergics mebeverine and alverine are not approved for use in the US. Mebeverine and alverine probably have similar efficacy to the anticholinergics in the management of IBS.

Peppermint oil has antispasmodic properties, and is recommended by both the ACG and AGA for the relief of global IBS symptoms.[39]​​[78][87]​​ It is available as drops or enteric-coated sustained-release tablets. Evidence is mixed. One meta-analysis found that peppermint oil reduced abdominal pain and overall IBS symptoms compared with placebo.[97] However, a subsequent randomised controlled trial (that employed end points recommended by regulatory authorities) concluded that peppermint oil does not significantly reduce abdominal pain or improve overall symptom relief.[98]

Primary options

dicycloverine: 10-20 mg orally three times daily as needed

OR

hyoscyamine: 0.125 to 0.25 mg orally/sublingually three to four times daily as needed, maximum 1.5 mg/day

OR

peppermint oil: consult product literature for guidance on dose

2nd line – lifestyle and dietary modifications

Back
ONGOING
|
constipation-predominant
|
with pain or bloating predominant
2nd line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce abdominal bloating and flatulence, alleviate pain, and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Plus – antidepressant

Back
ONGOING
|
constipation-predominant
|
with pain or bloating predominant
Plus – 

antidepressant

Treatment recommended for ALL patients in selected patient group

If pain persists despite antispasmodics, a tricyclic antidepressant (TCA) such as amitriptyline, nortriptyline, or desipramine, used as a gut-brain neuromodulator, may be beneficial.[39]​​​[78][87][99]​​​ TCAs are thought to improve visceral and central pain by acting on noradrenaline and dopaminergic receptors. They may also improve abdominal pain because of their anticholinergic effects. At higher doses they can slow gastrointestinal transit, which can be useful in patients with urgency and diarrhoea, but potentially problematic in patients with constipation. Secondary amine TCAs (e.g., desipramine and nortriptyline) may be better tolerated in patients with constipation-predominant IBS due to their lower anticholinergic effects.[78][87]​ Notable adverse events include dry mouth and eyes, urinary retention, cardiac arrhythmias, sedation, and constipation, so careful patient selection is needed.[39][87] The beneficial effects of TCAs on IBS symptoms appear to be independent of effects on depression and may take several weeks.[87]

Selective serotonin-reuptake inhibitors (SSRIs) are not recommended in US guidelines because of a lack of high-quality evidence that they significantly improve global symptoms or abdominal pain in patients with IBS.[39][87]​ In one meta-analysis, subgroup analysis by antidepressant class found no significant benefit from SSRIs in patients with IBS and abdominal pain; the beneficial effect on abdominal pain appeared to be limited to TCAs.[100] American Gastroenterological Association guidelines note that in some patients, however, SSRIs may improve the perception of overall IBS symptoms and well-being by improving gastrointestinal symptoms, mood, and extraintestinal symptoms.[87] UK guidelines differ from US guidelines, recommending that SSRIs can be used as an alternative to TCAs for treating global symptoms of IBS.[53]

Treatment should be started at low doses and titrated gradually according to response and tolerability.

Primary options

amitriptyline: 10 mg orally once daily initially, increase dose gradually according to response, maximum 100 mg/day

OR

nortriptyline: 10-25 mg orally once daily initially, increase dose gradually according to response, maximum 75 mg/day

OR

desipramine: 10 mg orally once daily initially, increase dose gradually according to response, maximum 100 mg/day

Secondary options

paroxetine: 20-40 mg orally once daily

OR

citalopram: 20-40 mg orally once daily

Plus – secretagogue

Back
ONGOING
|
constipation-predominant
|
with pain or bloating predominant
Plus – 

secretagogue

Treatment recommended for ALL patients in selected patient group

Lubiprostone, linaclotide, plecanatide, or tenapanor are secretagogues that are recommended for patients with persistent constipation despite treatment with initial laxatives.[39]​​[53][78]

One systematic review and network meta-analysis examining the relative efficacy of these secretagogues across 18 randomised controlled trials found that they were all superior to placebo.[79] Linaclotide was the most efficacious agent for relieving constipation; plecanatide had the best safety profile.[79] Analyses utilised data extracted at a 12-week timepoint; longer-term effects are unknown.

Linaclotide and plecanatide are minimally absorbed 14-amino acid peptides that bind and activate the guanylate cyclase C receptor on the luminal surface of the enterocyte. This results in increased levels of cyclic guanosine monophosphate (cGMP), a second messenger that increases secretion of intestinal fluid.[80] Plecanatide and linaclotide are comparably effective, safe, and well tolerated.[39][81] Diarrhoea is a common side effect of both these medications.[53]

Treatment with lubiprostone, a chloride-channel 2 (CIC2) activator, is an alternative in patients with constipation-predominant IBS who do not tolerate laxatives or stool softeners, or in whom these are ineffective.[39][82][83]​ Lubiprostone is approved by the US Food and Drug Administration (FDA) for the treatment of IBS with constipation only in women aged ≥18 years. Diarrhoea is a less common adverse effect with lubiprostone than with other secretagogues; however, patients should be warned that nausea is a frequent side effect.[53]

Tenapanor, an inhibitor of the sodium-proton exchanger NHE3, is another alternative. It is effective for constipation and other global symptoms of IBS like bloating. As with linaclotide and plecanatide, diarrhoea is a side effect.[53]

Primary options

lubiprostone: women: 8 micrograms orally twice daily

OR

linaclotide: 290 micrograms orally once daily

OR

plecanatide: 3 mg orally once daily

OR

tenapanor: 50 mg orally twice daily

Consider – psychological therapy

Back
ONGOING
|
constipation-predominant
|
with pain or bloating predominant
Consider – 

psychological therapy

Additional treatment recommended for SOME patients in selected patient group

Patients who do not respond to pharmacological treatment may need referral for more intensive psychological treatments and support.[34] One meta-analysis of randomised controlled trials of psychological therapies for IBS demonstrated that several types of therapy were more efficacious than control interventions. However, the most compelling evidence, based on the number of trials and long-term outcomes, was for IBS-specific cognitive behavioural therapy (CBT) and gut-directed hypnotherapy.[101] Both are recommended in US and UK guidelines; UK National Institute for Health and Care Excellence guidelines specify a role for them when symptoms have not improved after 12 months of pharmacological treatment, whereas American College of Gastroenterology guidelines recommend their use in conjunction with other IBS therapies for patients who are emotionally stable but exhibit cognitive-affective drivers of IBS.[34][39]​​

Patients with predominantly pain-related symptoms may need referral to a pain specialist or clinic.

3rd line – lifestyle and dietary modifications

Back
ONGOING
|
constipation-predominant
|
with pain or bloating predominant
3rd line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce abdominal bloating and flatulence, alleviate pain, and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Plus – antidepressant

Back
ONGOING
|
constipation-predominant
|
with pain or bloating predominant
Plus – 

antidepressant

Treatment recommended for ALL patients in selected patient group

If pain persists despite antispasmodics, a tricyclic antidepressant (TCA) such as amitriptyline, nortriptyline, or desipramine, used as a gut-brain neuromodulator, may be beneficial.[39][78]​​​​[87]​​​​[99]​​ TCAs are thought to improve visceral and central pain by acting on noradrenaline and dopaminergic receptors. They may also improve abdominal pain because of their anticholinergic effects. At higher doses they can slow gastrointestinal transit, which can be useful in patients with urgency and diarrhoea, but potentially problematic in patients with constipation. Secondary amine TCAs (e.g., desipramine and nortriptyline) may be better tolerated in patients with constipation-predominant IBS due to their lower anticholinergic effects.[78][87]​ Notable adverse events include dry mouth and eyes, urinary retention, cardiac arrhythmias, sedation, and constipation, so careful patient selection is needed.[39][87] The beneficial effects of TCAs on IBS symptoms appear to be independent of effects on depression and may take several weeks.[87]

Selective serotonin-reuptake inhibitors (SSRIs) are not recommended in US guidelines because of a lack of high-quality evidence that they significantly improve global symptoms or abdominal pain in patients with IBS.[39][87]​ In one meta-analysis, subgroup analysis by antidepressant class found no significant benefit from SSRIs in patients with IBS and abdominal pain; the beneficial effect on abdominal pain appeared to be limited to TCAs.[100] American Gastroenterological Association guidelines note that in some patients, however, SSRIs may improve the perception of overall IBS symptoms and well-being by improving gastrointestinal symptoms, mood, and extraintestinal symptoms.[87] UK guidelines differ from US guidelines, recommending that SSRIs can be used as an alternative to TCAs for treating global symptoms of IBS.[53]

Treatment should be started at low doses and titrated gradually according to response and tolerability.

Primary options

amitriptyline: 10 mg orally once daily initially, increase dose gradually according to response, maximum 100 mg/day

OR

nortriptyline: 10-25 mg orally once daily initially, increase dose gradually according to response, maximum 75 mg/day

OR

desipramine: 10 mg orally once daily initially, increase dose gradually according to response, maximum 100 mg/day

Secondary options

paroxetine: 20-40 mg orally once daily

OR

citalopram: 20-40 mg orally once daily

Consider – psychological therapies

Back
ONGOING
|
constipation-predominant
|
with pain or bloating predominant
Consider – 

psychological therapies

Additional treatment recommended for SOME patients in selected patient group

Patients who do not respond to pharmacological treatment may need referral for more intensive psychological treatments and support.[34] One meta-analysis of randomised controlled trials of psychological therapies for IBS demonstrated that several types of therapy were more efficacious than control interventions. However, the most compelling evidence, based on the number of trials and long-term outcomes, was for IBS-specific cognitive behavioural therapy (CBT) and gut-directed hypnotherapy.[101] Both are recommended in US and UK guidelines; UK National Institute for Health and Care Excellence guidelines specify a role for them when symptoms have not improved after 12 months of pharmacological treatment, whereas American College of Gastroenterology guidelines recommend their use in conjunction with other IBS therapies for patients who are emotionally stable but exhibit cognitive-affective drivers of IBS.[34][39]​​

Patients with predominantly pain-related symptoms may need referral to a pain specialist or clinic.

diarrhoea-predominant

1st line – lifestyle and dietary modifications

Back
ONGOING
|
diarrhoea-predominant
|
pain or bloating not predominant
1st line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce flatulence and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Plus – antidiarrhoeal

Back
ONGOING
|
diarrhoea-predominant
|
pain or bloating not predominant
Plus – 

antidiarrhoeal

Treatment recommended for ALL patients in selected patient group

Loperamide and opioid agonists/antagonists (e.g., eluxadoline) are variously recommended for patients with diarrhoea-predominant IBS (IBS-D).[34][39][87]

Loperamide is a synthetic peripheral opioid agonist. It inhibits peristalsis and antisecretory activity and prolongs intestinal transit time with limited penetrance of the blood-brain barrier.[87] The American College of Gastroenterology (ACG) and American Gastroenterological Association (AGA) both note that loperamide improves diarrhoea but not global IBS symptoms.[39][87]

Eluxadoline is a minimally absorbed mixed opioid receptor agonist and antagonist that was developed to reduce abdominal pain and diarrhoea in patients who have IBS-D, without constipating side effects.[88] In studies it has demonstrated significant improvements in stool consistency and urgency, but less effect on abdominal pain. It may therefore be more useful in patients with IBS-D with predominant and troublesome diarrhoea than in those with predominant or more severe abdominal pain.[87] Eluxadoline is contraindicated in patients without a gallbladder or in patients who drink more than 3 alcoholic beverages per day because of increased risk of pancreatitis resulting in hospitalisation or death.[89]

Colestyramine may be more effective than loperamide in patients who have had a cholecystectomy. If bile acid-related diarrhoea is suspected, a trial of colestyramine may be warranted, either empirically or following testing if available.[40]

Alosetron and rifaximin are recommended for the management of IBS-D in patients whose symptoms persist despite treatment with loperamide or an opioid agonist/antagonist.[39][87]

Alosetron is a 5-HT3 antagonist; these have been shown to significantly improve symptoms in patients with IBS-D.[90][91]

Availability of alosetron may be restricted due to safety concerns. It was originally approved by the US Food and Drug Administration (FDA) in 2000 for the treatment of IBS-D in women; however, it was voluntarily withdrawn due to serious adverse events, particularly ischaemic colitis and serious complications of constipation.[87][91][92]​​​​ It was reintroduced in 2002, but with use restricted to the treatment of severe IBS-D in women under a risk management programme. Though safety risks with alosetron still exist, the FDA has discontinued the risk management programme. Counselling patients on the signs and symptoms of serious complications of constipation and ischaemic colitis is recommended. Immediate discontinuation of treatment is recommended in patients with signs or symptoms of ischaemic colitis. Alosetron is only recommended for women with severe, diarrhoea-predominant IBS who have had symptoms for 6 months or longer, do not have physical or biochemical abnormalities of the gastrointestinal tract, and have not responded adequately to conventional treatment.[39][87]​​ Severe symptoms are defined as 1 or more of the following: frequent and severe abdominal pain/discomfort, frequent bowel urgency or faecal incontinence, and/or disability or restriction of daily activities due to IBS.[87]

Rifaximin, a minimally absorbed broad-spectrum oral antibiotic, has been shown to reduce global symptoms, bloating, abdominal pain, and loose watery stools in patients with IBS without constipation.​[72][87]​​[93][94][95] Rifaximin has been approved by the FDA as a 14-day course for the treatment of diarrhoea-predominant IBS. For recurrent symptoms, up to three courses are approved.

Primary options

loperamide: 2-4 mg orally initially, followed by 2 mg after each loose stool when required, maximum 16 mg/day

OR

colestyramine: 2-4 g orally two to four times daily

OR

eluxadoline: 75-100 mg orally twice daily

Secondary options

alosetron: 0.5 to 1 mg orally twice daily

OR

rifaximin: 550 mg orally three times daily for 14 days; course may be repeated twice if recurrent symptoms

1st line – lifestyle and dietary modifications

Back
ONGOING
|
diarrhoea-predominant
|
pain or bloating predominant
1st line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce abdominal bloating and flatulence, alleviate pain, and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Plus – antidiarrhoeal

Back
ONGOING
|
diarrhoea-predominant
|
pain or bloating predominant
Plus – 

antidiarrhoeal

Treatment recommended for ALL patients in selected patient group

Loperamide and opioid agonists/antagonists (e.g., eluxadoline) are variously recommended for patients with diarrhoea-predominant IBS (IBS-D).[34][39][87]

Loperamide is a synthetic peripheral opioid agonist. It inhibits peristalsis and antisecretory activity and prolongs intestinal transit time with limited penetrance of the blood-brain barrier.[87] The American College of Gastroenterology (ACG) and American Gastroenterological Association (AGA) both note that loperamide improves diarrhoea but not global IBS symptoms.[39][87]

Eluxadoline is a minimally absorbed mixed opioid receptor agonist and antagonist that was developed to reduce abdominal pain and diarrhoea in patients who have IBS-D, without constipating side effects.[88] In studies it has demonstrated significant improvements in stool consistency and urgency, but less effect on abdominal pain. It may therefore be more useful in patients with IBS-D with predominant and troublesome diarrhoea than in those with predominant or more severe abdominal pain.[87] Eluxadoline is contraindicated in patients without a gallbladder or in patients who drink more than 3 alcoholic beverages per day because of increased risk of pancreatitis resulting in hospitalisation or death.[89]

Colestyramine may be more effective than loperamide in patients who have had a cholecystectomy. If bile acid-related diarrhoea is suspected, a trial of colestyramine may be warranted, either empirically or following testing if available.[40]

Alosetron and rifaximin are recommended for the management of IBS-D in patients whose symptoms persist despite treatment with loperamide or an opioid agonist/antagonist.[39][87]

Alosetron is a 5-HT3 antagonist; these have been shown to significantly improve symptoms in patients with IBS-D.[90][91]

Availability of alosetron may be restricted due to safety concerns. It was originally approved by the US Food and Drug Administration (FDA) in 2000 for the treatment of IBS-D in women; however, it was voluntarily withdrawn due to serious adverse events, particularly ischaemic colitis and serious complications of constipation.[87][91][92]​​​​ It was reintroduced in 2002, but with use restricted to the treatment of severe IBS-D in women under a risk management programme. Though safety risks with alosetron still exist, the FDA has discontinued the risk management programme. Counselling patients on the signs and symptoms of serious complications of constipation and ischaemic colitis is recommended. Immediate discontinuation of treatment is recommended in patients with signs or symptoms of ischaemic colitis. Alosetron is only recommended for women with severe, diarrhoea-predominant IBS who have had symptoms for 6 months or longer, do not have physical or biochemical abnormalities of the gastrointestinal tract, and have not responded adequately to conventional treatment.[39][87]​​ Severe symptoms are defined as 1 or more of the following: frequent and severe abdominal pain/discomfort, frequent bowel urgency or faecal incontinence, and/or disability or restriction of daily activities due to IBS.[87]

Rifaximin, a minimally absorbed broad-spectrum oral antibiotic, has been shown to reduce global symptoms, bloating, abdominal pain, and loose watery stools in patients with IBS without constipation.​[72][87]​​[93][94][95] Rifaximin has been approved by the FDA as a 14-day course for the treatment of diarrhoea-predominant IBS. For recurrent symptoms, up to three courses are approved.

Primary options

loperamide: 2-4 mg orally initially, followed by 2 mg after each loose stool when required, maximum 16 mg/day

OR

colestyramine: 2-4 g orally two to four times daily

OR

eluxadoline: 75-100 mg orally twice daily

Secondary options

alosetron: 0.5 to 1 mg orally twice daily

OR

rifaximin: 550 mg orally three times daily for 14 days; course may be repeated twice if recurrent symptoms

Plus – antispasmodic

Back
ONGOING
|
diarrhoea-predominant
|
pain or bloating predominant
Plus – 

antispasmodic

Treatment recommended for ALL patients in selected patient group

Antispasmodics may be considered for patients experiencing pain or bloating.[34][87] They act by relaxing smooth muscle, thereby reducing gut motility. One Cochrane review found that patients taking antispasmodics experienced significantly greater improvement in both abdominal pain and global IBS symptoms.[76] The effect of individual antispasmodics was difficult to interpret, however, because of the inclusion of 12 different drugs and the small number of studies evaluated for each drug. There was also considerable variation between the studies concerning diagnostic and inclusion criteria, dosing schedule, and study end points.[87]

Because of the lack of high-quality evidence available, American College of Gastroenterology (ACG) guidelines recommend against the use of antispasmodics currently available in the US to treat global IBS symptoms (dicyclomine and hyoscyamine). They concede that there are more robust data supporting the use of alternative antispasmodics available internationally.[39] The American Gastroenterological Association (AGA) differs in its guidance and does recommend hyoscyamine and dicyclomine.[78][87]​​

Not all antispasmodic agents are universally available; for example, the non-anticholinergics mebeverine and alverine are not approved for use in the US. Mebeverine and alverine probably have similar efficacy to the anticholinergics in the management of IBS.

Peppermint oil has antispasmodic properties, and is recommended by both the ACG and AGA for the relief of global IBS symptoms.[39][78]​​[87]​​ It is available as drops or enteric-coated sustained-release tablets. Evidence is mixed. One meta-analysis found that peppermint oil reduced abdominal pain and overall IBS symptoms compared with placebo.[97] However, a subsequent randomised controlled trial (that employed end points recommended by regulatory authorities) concluded that peppermint oil does not significantly reduce abdominal pain or improve overall symptom relief.[98]

Primary options

dicycloverine: 10-20 mg orally three times daily as needed

OR

hyoscyamine: 0.125 to 0.25 mg orally/sublingually three to four times daily as needed, maximum 1.5 mg/day

OR

peppermint oil: consult product literature for guidance on dose

2nd line – lifestyle and dietary modifications

Back
ONGOING
|
diarrhoea-predominant
|
pain or bloating predominant
2nd line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce abdominal bloating and flatulence, alleviate pain, and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Plus – antidepressant

Back
ONGOING
|
diarrhoea-predominant
|
pain or bloating predominant
Plus – 

antidepressant

Treatment recommended for ALL patients in selected patient group

If pain persists despite antispasmodics, a tricyclic antidepressant (TCA) such as amitriptyline, nortriptyline, or desipramine, used as a gut-brain neuromodulator, may be beneficial.[39][78]​​​[87]​​[99]​​ TCAs are thought to improve visceral and central pain by acting on noradrenaline and dopaminergic receptors. They may also improve abdominal pain because of their anticholinergic effects. At higher doses they can slow gastrointestinal transit, which can be useful in patients with urgency and diarrhoea, but potentially problematic in patients with constipation. Secondary amine TCAs (e.g., desipramine and nortriptyline) may be better tolerated in patients with constipation-predominant IBS due to their lower anticholinergic effects.[78][87]​ Notable adverse events include dry mouth and eyes, urinary retention, cardiac arrhythmias, sedation, and constipation, so careful patient selection is needed.[39][87] The beneficial effects of TCAs on IBS symptoms appear to be independent of effects on depression and may take several weeks.[87]

Selective serotonin-reuptake inhibitors (SSRIs) are not recommended in US guidelines because of a lack of high-quality evidence that they significantly improve global symptoms or abdominal pain in patients with IBS.[39][87]​ In one meta-analysis, subgroup analysis by antidepressant class found no significant benefit from SSRIs in patients with IBS and abdominal pain; the beneficial effect on abdominal pain appeared to be limited to TCAs.[100] American Gastroenterological Association guidelines note that in some patients, however, SSRIs may improve the perception of overall IBS symptoms and well-being by improving gastrointestinal symptoms, mood, and extraintestinal symptoms.[87] UK guidelines differ from US guidelines, recommending that SSRIs can be used as an alternative to TCAs for treating global symptoms of IBS.[53]

Treatment should be started at low doses and titrated gradually according to response and tolerability.

Primary options

amitriptyline: 10 mg orally once daily initially, increase dose gradually according to response, maximum 100 mg/day

OR

nortriptyline: 10-25 mg orally once daily initially, increase dose gradually according to response, maximum 75 mg/day

OR

desipramine: 10 mg orally once daily initially, increase dose gradually according to response, maximum 100 mg/day

Secondary options

paroxetine: 20-40 mg orally once daily

OR

citalopram: 20-40 mg orally once daily

Consider – psychological therapy

Back
ONGOING
|
diarrhoea-predominant
|
pain or bloating predominant
Consider – 

psychological therapy

Additional treatment recommended for SOME patients in selected patient group

Patients who do not respond to pharmacological treatment may need referral for more intensive psychological treatments and support.[34] One meta-analysis of randomised controlled trials of psychological therapies for IBS demonstrated that several types of therapy were more efficacious than control interventions. However, the most compelling evidence, based on the number of trials and long-term outcomes, was for IBS-specific cognitive behavioural therapy (CBT) and gut-directed hypnotherapy.[101] Both are recommended in US and UK guidelines; UK National Institute for Health and Care Excellence guidelines specify a role for them when symptoms have not improved after 12 months of pharmacological treatment, whereas American College of Gastroenterology guidelines recommend their use in conjunction with other IBS therapies for patients who are emotionally stable but exhibit cognitive-affective drivers of IBS.​[34][39]

Patients with predominantly pain-related symptoms may need referral to a pain specialist or clinic.

alternating constipation and diarrhoea

1st line – lifestyle and dietary modifications

Back
ONGOING
|
alternating constipation and diarrhoea
|
pain or bloating not predominant
1st line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce flatulence and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Consider – laxative

Back
ONGOING
|
alternating constipation and diarrhoea
|
pain or bloating not predominant
Consider – 

laxative

Additional treatment recommended for SOME patients in selected patient group

The American Gastroenterological Association suggests that polyethylene glycol (PEG) may be used for specific symptom relief, or as adjunctive therapy for the treatment of IBS with constipation (IBS-C).[78] American College of Gastroenterology guidelines contradict this, however, citing a lack of evidence that PEG alleviates abdominal pain, and thus global symptoms, in patients with IBS-C.[39] They therefore recommend against the use of PEG alone for the treatment of global IBS-C symptoms, although they recognise that clinicians may use PEG as first-line treatment of constipation in IBS, given its low cost and availability.[39]

Consider – loperamide

Back
ONGOING
|
alternating constipation and diarrhoea
|
pain or bloating not predominant
Consider – 

loperamide

Additional treatment recommended for SOME patients in selected patient group

Loperamide should be used when needed in a diarrhoeal phase.

Long-term use of antidiarrhoeals should be monitored.

Primary options

loperamide: 2-4 mg orally initially, followed by 2 mg after each loose stool when required, maximum 16 mg/day

1st line – lifestyle and dietary modifications

Back
ONGOING
|
alternating constipation and diarrhoea
|
pain or bloating predominant
1st line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce abdominal bloating and flatulence, alleviate pain, and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Plus – antispasmodic

Back
ONGOING
|
alternating constipation and diarrhoea
|
pain or bloating predominant
Plus – 

antispasmodic

Treatment recommended for ALL patients in selected patient group

Antispasmodics may be considered for patients experiencing pain or bloating.[34][87] They act by relaxing smooth muscle, thereby reducing gut motility. One Cochrane review found that patients taking antispasmodics experienced significantly greater improvement in both abdominal pain and global IBS symptoms.[76] The effect of individual antispasmodics was difficult to interpret, however, because of the inclusion of 12 different drugs and the small number of studies evaluated for each drug. There was also considerable variation between the studies concerning diagnostic and inclusion criteria, dosing schedule, and study end points.[87]

Because of the lack of high-quality evidence available, American College of Gastroenterology (ACG) guidelines recommend against the use of antispasmodics currently available in the US to treat global IBS symptoms (dicyclomine and hyoscyamine). They concede that there are more robust data supporting the use of alternative antispasmodics available internationally.[39] The American Gastroenterological Association (AGA) differs in its guidance and does recommend hyoscyamine and dicyclomine.​[78][87]

Not all antispasmodic agents are universally available; for example, the non-anticholinergics mebeverine and alverine are not approved for use in the US. Mebeverine and alverine probably have similar efficacy to the anticholinergics in the management of IBS.

Peppermint oil has antispasmodic properties, and is recommended by both the ACG and AGA for the relief of global IBS symptoms.[39]​​[78][87]​​ It is available as drops or enteric-coated sustained-release tablets. Evidence is mixed. One meta-analysis found that peppermint oil reduced abdominal pain and overall IBS symptoms compared with placebo.[97] However, a subsequent randomised controlled trial (that employed end points recommended by regulatory authorities) concluded that peppermint oil does not significantly reduce abdominal pain or improve overall symptom relief.[98]

Primary options

dicycloverine: 10-20 mg orally three times daily as needed

OR

hyoscyamine: 0.125 to 0.25 mg orally/sublingually three to four times daily as needed, maximum 1.5 mg/day

OR

peppermint oil: consult product literature for guidance on dose

Consider – laxative

Back
ONGOING
|
alternating constipation and diarrhoea
|
pain or bloating predominant
Consider – 

laxative

Additional treatment recommended for SOME patients in selected patient group

The American Gastroenterological Association suggests that polyethylene glycol (PEG) may be used for specific symptom relief, or as adjunctive therapy for the treatment of IBS with constipation (IBS-C).[78] American College of Gastroenterology guidelines contradict this, however, citing a lack of evidence that PEG alleviates abdominal pain, and thus global symptoms, in patients with IBS-C.[39] They therefore recommend against the use of PEG alone for the treatment of global IBS-C symptoms, although they recognise that clinicians may use PEG as first-line treatment of constipation in IBS, given its low cost and availability.[39]

Consider – loperamide

Back
ONGOING
|
alternating constipation and diarrhoea
|
pain or bloating predominant
Consider – 

loperamide

Additional treatment recommended for SOME patients in selected patient group

Loperamide should be used when needed in a diarrhoeal phase.

Long-term use of antidiarrhoeals should be monitored.

Primary options

loperamide: 2-4 mg orally initially, followed by 2 mg after each loose stool when required, maximum 16 mg/day

2nd line – lifestyle and dietary modifications

Back
ONGOING
|
alternating constipation and diarrhoea
|
pain or bloating predominant
2nd line – 

lifestyle and dietary modifications

In all patients, an effective therapeutic relationship should be established, followed by education and reassurance.

Initial treatments should be conservative, including discussion of lifestyle changes that may lessen stress.

Possible precipitating substances such as caffeine, lactose, or fructose may need to be eliminated from the diet. UK guidelines recommend that all patients should be advised of the potential benefits of regular exercise, citing evidence from randomised controlled trials (RCTs) that this can be beneficial, particularly for constipation.[53] However, US guidelines do not recommend exercise as a treatment.[39] One Cochrane review reported that physical activity may improve symptoms, but not quality of life or abdominal pain, in people with IBS.[54]

Dietary advice should be given to all patients who can associate triggering or worsening of their IBS symptoms with eating food (this encompasses over 80% of patients with IBS) and who are motivated to make the necessary changes.[55] Referral to a registered dietitian nutritionist (RDN) should be made for patients who are willing to engage and patients who are not able to implement recommended dietary changes on their own.[55]

A trial of a low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) diet is recommended.[34][39][53] The low FODMAP diet is currently the most evidence-based diet for treating IBS.

FODMAPs are poorly absorbed short-chain carbohydrates that are prone to cause symptoms in patients with IBS. The low FODMAP diet induces favourable changes in the intestinal microbiota and significantly diminishes histamine, which may play a provocative role in some patients.[56][57]

A diet low in FODMAPs has been shown to improve multiple symptoms, including diarrhoea, flatus, bloating, and pain.[58][59][60][61][62]​​ However, RCTs have typically been of short duration and at risk of bias.[63][64]

One meta-analysis showed significant superiority of a low FODMAP diet over British Dietetic Association dietary advice in reducing abdominal pain, bloating, and distension.[65] One European randomised trial found that in patients with IBS in primary care, a smartphone FODMAP-lowering diet application was superior to an antispasmodic agent in improving IBS symptoms. The authors concluded that a low FODMAP diet should be considered the first-line treatment for IBS in primary care.[66] However, it is uncertain which patients respond to specific FODMAP restrictions and adherence can be an issue. Clinicians should consider an individualised approach to the low FODMAP diet, such as dietary restriction relevant to the patients' ethnicity, symptom profile, and usual dietary intake.[67]

Before recommending a restrictive diet of this nature, it is important to exclude disordered eating behaviours and eating disorders through careful history taking, as these are common in patients with gastrointestinal disorders.[55] Screening for malnutrition using a validated screening tool should also be considered. If the results indicate malnutrition, the patient is not suitable for dietary restrictions and should be referred to an RDN for a comprehensive nutritional assessment.[55]

A low FODMAP diet consists of three phases: restriction of FODMAP foods (lasting no more than 4-6 weeks); reintroduction of FODMAP foods; and personalisation of ongoing diet based on the outcome of reintroduction. These diet interventions should be attempted for a predetermined time period, and ideally supervised by a registered dietitian, although in some cases this may not be practical or affordable.[55] Studies have demonstrated that 4-6 weeks of a low FODMAP diet is sufficient to determine whether a patient is going to respond.[55]

It remains unclear whether a gluten-free diet is of similar benefit to patients with IBS, with mixed results from RCTs.[55][68][69] Currently, a gluten-free diet is not recommended for the treatment of IBS.[53]

If the patient has constipation or alternating constipation and diarrhoea, then soluble fibre (found in ispaghula, oat bran, barley, and beans) is often recommended. People with IBS should avoid insoluble fibre.[34][39][55] One UK guideline advises starting soluble fibre at a low dose (3-4 g/day) and building up gradually to avoid bloating.[53]

Effectiveness has not been consistently demonstrated, but the lack of significant adverse effects makes soluble fibre a reasonable first-line therapy for patients with IBS with symptoms.[7][39][75][76][77]​​​

Probiotics may also be considered. Probiotics can help reduce abdominal bloating and flatulence, alleviate pain, and improve quality of life.[70]​ Response to probiotics varies between studies and individuals.[71][72]​ They are not routinely recommended due to the heterogeneity in trials regarding outcome, design, magnitude of benefit, and uncertainty regarding the most effective strain.[39][73]

Systematic review and meta-analyses indicate that composite probiotics containing Bifidobacterium infantis may be more effective than single strain probiotic therapy.[71][74]

If a patient chooses to try probiotics, one UK guideline recommends taking them for up to 12 weeks at the dose recommended by the manufacturer, and discontinuing treatment if there is no improvement in symptoms.[55]

Plus – antidepressant

Back
ONGOING
|
alternating constipation and diarrhoea
|
pain or bloating predominant
Plus – 

antidepressant

Treatment recommended for ALL patients in selected patient group

If pain persists despite antispasmodics, a tricyclic antidepressant (TCA) such as amitriptyline, nortriptyline, or desipramine, used as a gut-brain neuromodulator, may be beneficial.[39][78]​​​[87][99]​​ TCAs are thought to improve visceral and central pain by acting on noradrenaline and dopaminergic receptors. They may also improve abdominal pain because of their anticholinergic effects. At higher doses they can slow gastrointestinal transit, which can be useful in patients with urgency and diarrhoea, but potentially problematic in patients with constipation. Secondary amine TCAs (e.g., desipramine and nortriptyline) may be better tolerated in patients with constipation-predominant IBS due to their lower anticholinergic effects.[78][87]​ Notable adverse events include dry mouth and eyes, urinary retention, cardiac arrhythmias, sedation, and constipation, so careful patient selection is needed.[39][87] The beneficial effects of TCAs on IBS symptoms appear to be independent of effects on depression and may take several weeks.[87]

Selective serotonin-reuptake inhibitors (SSRIs) are not recommended in US guidelines because of a lack of high-quality evidence that they significantly improve global symptoms or abdominal pain in patients with IBS.[39][87]​ In one meta-analysis, subgroup analysis by antidepressant class found no significant benefit from SSRIs in patients with IBS and abdominal pain; the beneficial effect on abdominal pain appeared to be limited to TCAs.[100] American Gastroenterological Association guidelines note that in some patients, however, SSRIs may improve the perception of overall IBS symptoms and well-being by improving gastrointestinal symptoms, mood, and extraintestinal symptoms.[87] UK guidelines differ from US guidelines, recommending that SSRIs can be used as an alternative to TCAs for treating global symptoms of IBS.[53]

Treatment should be started at low doses and titrated gradually according to response and tolerability.

Primary options

amitriptyline: 10 mg orally once daily initially, increase dose gradually according to response, maximum 100 mg/day

OR

nortriptyline: 10-25 mg orally once daily initially, increase dose gradually according to response, maximum 75 mg/day

OR

desipramine: 10 mg orally once daily initially, increase dose gradually according to response, maximum 100 mg/day

Secondary options

paroxetine: 20-40 mg orally once daily

OR

citalopram: 20-40 mg orally once daily

Consider – psychological therapy

Back
ONGOING
|
alternating constipation and diarrhoea
|
pain or bloating predominant
Consider – 

psychological therapy

Additional treatment recommended for SOME patients in selected patient group

Patients who do not respond to pharmacological treatment may need referral for more intensive psychological treatments and support.[34] One meta-analysis of randomised controlled trials of psychological therapies for IBS demonstrated that several types of therapy were more efficacious than control interventions. However, the most compelling evidence, based on the number of trials and long-term outcomes, was for IBS-specific cognitive behavioural therapy (CBT) and gut-directed hypnotherapy.[101] Both are recommended in US and UK guidelines; UK National Institute for Health and Care Excellence guidelines specify a role for them when symptoms have not improved after 12 months of pharmacological treatment, whereas American College of Gastroenterology guidelines recommend their use in conjunction with other IBS therapies for patients who are emotionally stable but exhibit cognitive-affective drivers of IBS.[34][39]​​

Patients with predominantly pain-related symptoms may need referral to a pain specialist or clinic.

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Please note that formulations/routes and doses may differ between drug names and brands, drug formularies, or locations. Treatment recommendations are specific to patient groups. See disclaimer

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