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

INITIAL

high-altitude ascent planned

1st line – prophylactic nonpharmacologic measures

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INITIAL
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high-altitude ascent planned
1st line – 

prophylactic nonpharmacologic measures

Once above 3000 m (about 9840 feet), individuals should ascend no more than 500 m (about 1600 feet) in any 24-hour period, and undertake a rest day every 3-4 days of ascent.[7][29]

Avoiding strenuous activity on arrival and maintaining adequate hydration are also thought to limit the incidence of high-altitude illness.[3][85]

Plus – acetazolamide or dexamethasone

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INITIAL
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high-altitude ascent planned
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with rapid ascent planned or known AMS susceptibility
Plus – 

acetazolamide or dexamethasone

Treatment recommended for ALL patients in selected patient group

If a rapid ascent is planned, or the patient has known susceptibility to acute mountain sickness (AMS), acetazolamide is the preferred prophylactic agent.[37][38][39][40]​​

Dexamethasone is an alternative choice for those who are allergic to or intolerant of acetazolamide.[29][40][41]​​ Both have been shown to prevent the symptoms of AMS.[17][37][73][74]​​

Medications are usually started at least 1 day prior to ascent and continued until acclimatization is deemed to be complete. If dexamethasone is used for longer than 10 days, medication should be tapered over one week rather than stopped abruptly to avoid risk of adrenal suppression.[29]

Dexamethasone should also not be used for prophylaxis in children due to the potential for side effects unique to this population and the availability of other safe alternatives: namely, graded ascent and acetazolamide.​[29]

Regular doses of acetazolamide have been shown to be effective;​​​ however, higher doses are associated with side effects such as paresthesias, commonly experienced in the hands and feet.[41][76][77][78]​​

Primary options

acetazolamide: children: 2.5 mg/kg orally (immediate-release) every 12 hours, maximum 125 mg/dose; adults: 125 mg orally (immediate-release) twice daily, or 500 mg orally (extended-release) once or twice daily

Secondary options

dexamethasone: adults: 2 mg orally every 6 hours, or 4 mg every 6-12 hours

Plus – nifedipine

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INITIAL
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high-altitude ascent planned
|
with previous HAPE episode
Plus – 

nifedipine

Treatment recommended for ALL patients in selected patient group

Nifedipine has been shown to reduce the incidence of high-altitude pulmonary edema (HAPE) in individuals with a previous history of radiographically documented disease.[45] Extended-release preparations are preferred, and should be started 24 hours prior to ascent and continued until return to a low altitude.[7][29]​​

Primary options

nifedipine: children: consult specialist for guidance on dose; adults: 30 mg orally (extended-release) every 12 hours

ACUTE

AMS

1st line – rest ± descent or simulated descent

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ACUTE
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AMS
1st line – 

rest ± descent or simulated descent

In the event of acute mountain sickness (AMS), sufferers need to stop, rest, treat their symptoms, and descend if improvements do not occur (the STOP, REST, TREAT, DESCEND approach). In mild cases it may be enough to rest for a few days and treat symptoms with simple analgesia and antiemetics.

Patients with AMS can resume their ascent once symptoms resolve, and it is advisable to use pharmacologic prophylaxis before continuing. Further ascent or re-ascent to a previously attained altitude must not be attempted in the presence of continuing symptoms.

However, in those who fail to improve within 12-24 hours, descent is usually necessary and any further ascent should be made with the utmost caution. Often a descent of only a few hundred meters can improve symptoms.

AMS can also be treated with supplemental oxygen (2-4 L/minute) and portable hyperbaric therapy. Unfortunately, their effects are short-lived and symptoms tend to return within a few hours of stopping treatment.[86]

Consider – analgesia

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ACUTE
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AMS
Consider – 

analgesia

Treatment recommended for SOME patients in selected patient group

Headache should be treated with analgesics. There is anecdotal evidence to suggest that a significant risk of gastrointestinal bleeding exists at altitude.[80] It is therefore recommended that aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen are used with caution at altitude.

In a prospective randomized clinical trial with a field-based, double-blinded design, ibuprofen effectively reduced symptoms such as headaches and nausea.[87]

Primary options

acetaminophen: children: 10-15 mg/kg orally every 4-6 hours when required, maximum 75 mg/kg/day; adults: 325-1000 mg orally every 4-6 hours when required, maximum 4000 mg/day

Secondary options

ibuprofen: children ≥6 months of age: 5-10 mg/kg orally every 6-8 hours when required, maximum 40 mg/kg/day; adults: 400 mg orally every 4-6 hours when required, maximum 3200 mg/day

OR

aspirin: children: 10-15 mg/kg orally every 4-6 hours when required, maximum 60-80 mg/kg/day; adults: 325-650 mg orally every 4-6 hours when required, maximum 4000 mg/day

Consider – antiemetic

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ACUTE
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AMS
Consider – 

antiemetic

Treatment recommended for SOME patients in selected patient group

Antiemetics can be used to treat symptoms of nausea and vomiting.

Metoclopramide was found to be effective at reducing symptoms, including headache and nausea, in a prospective, double-blinded, randomized, field-based clinical trial.[87]

Primary options

prochlorperazine maleate: children: ≥2 years of age and 9-13 kg body weight: 2.5 mg orally every 12-24 hours when required, maximum 7.5 mg/day; children: ≥2 years of age and 14-17 kg body weight: 2.5 mg orally every 8-12 hours when required, maximum 10 mg/day; children: ≥2 years of age and 18-39 kg body weight: 2.5 mg orally every 8 hours or 5 mg every 12 hours when required, maximum 15 mg/day; children: ≥2 years of age and >39 kg body weight: 5 mg orally every 6-8 hours when required, maximum 20 mg/day; adults: 5-10 mg orally every 6-8 hours when required, maximum 40 mg/day

OR

promethazine: children ≥2 years of age: 0.25 to 1 mg/kg orally/intramuscularly/intravenously every 4-6 hours when required, maximum 25 mg/dose and 100 mg/day; adults: 12.5 to 25 mg orally/intramuscularly/intravenously, every 4-6 hours when required, maximum 100 mg/day

OR

ondansetron: children: consult specialist for guidance on dose; adults: 4-8 mg orally/intravenously every 8 hours when required, maximum 24 mg/day

OR

metoclopramide: children: consult specialist for guidance on dose; adults: 5-10 mg orally/intramuscularly/intravenously every 6-8 hours when required, maximum 45 mg/day

Consider – acetazolamide or hypnotic

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ACUTE
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AMS
Consider – 

acetazolamide or hypnotic

Treatment recommended for SOME patients in selected patient group

Acetazolamide or a hypnotic may be used to treat sleep disturbances.

Acetazolamide is often used to successfully treat episodes of periodic breathing that are commonly seen during sleep at altitude.[88]

In cases of intolerance or allergy to acetazolamide, hypnotics such as temazepam and zolpidem have been used successfully at altitude without causing respiratory depression.[89][90]​ Hypnotics are not approved for use in children.

Regular doses of acetazolamide have been shown to be effective;​​​ however, higher doses are associated with side effects such as paresthesias, commonly experienced in the hands and feet.[41][76][77][78]​​

Primary options

acetazolamide: children: 2.5 mg/kg orally (immediate-release) every 12 hours, maximum 250 mg/dose; adults: 250 mg orally (immediate-release) every 12 hours

OR

temazepam: adults: 10 mg orally once daily at night

OR

zolpidem: adults: 5 mg orally (immediate-release) once daily at bedtime when required; 6.25 mg orally (extended-release) once daily at bedtime when required; higher doses may cause next-morning drowsiness and are not recommended, especially in women

2nd line – acetazolamide or dexamethasone

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ACUTE
|
AMS
2nd line – 

acetazolamide or dexamethasone

Acetazolamide or dexamethasone may be used to treat acute mountain sickness (AMS) if patients are refractory to rest and symptomatic treatment; however, these may take several hours to work and can initially worsen symptoms.[79][83][84]

Regular doses of acetazolamide have been shown to be effective;​​ however, higher doses are associated with side effects such as paresthesias, commonly experienced in the hands and feet.[41][76][77][78]​​

Primary options

acetazolamide: children: 2.5 mg/kg orally (immediate-release) every 12 hours, maximum 250 mg/dose; adults: 250 mg orally (immediate-release) every 12 hours

OR

dexamethasone: children: 0.15 mg/kg orally every 6 hours, maximum 4 mg/dose; adults: 8 mg orally initially, followed by 4 mg every 6 hours

OR

dexamethasone sodium phosphate: children: 0.15 mg/kg intramuscularly/intravenously every 6 hours, maximum 4 mg/dose; adults: 8 mg intramuscularly/intravenously initially, followed by 4 mg every 6 hours

Plus – descent or simulated descent

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ACUTE
|
AMS
Plus – 

descent or simulated descent

Treatment recommended for ALL patients in selected patient group

In those who fail to improve within 12-24 hours, descent is usually necessary. Often a descent of only a few hundred metres can improve symptoms.

AMS can also be treated with supplemental oxygen (2-4 L/min) and portable hyperbaric therapy. Unfortunately, their effects are short-lived and symptoms tend to return within a few hours of stopping treatment.[86]

HAPE only

1st line – descent or simulated descent

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ACUTE
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HAPE only
1st line – 

descent or simulated descent

Ideally, those with high-altitude pulmonary edema (HAPE) should descend quickly to low altitude.

In the event of any delay, the partial pressure of inspired oxygen (PIO2) can be increased by using supplemental oxygen (face mask or nasal prongs 2-4 L/minute), or a portable hyperbaric chamber (2 psi - 13.8 KPa).[7]

A combination of supplemental oxygen and portable hyperbaric treatment can be used in severe cases.[91]

Plus – nifedipine

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ACUTE
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HAPE only
Plus – 

nifedipine

Treatment recommended for ALL patients in selected patient group

Nifedipine is able to inhibit hypoxic pulmonary vasoconstriction and reduce pulmonary artery pressure.​​[3] It can therefore be used in both prophylaxis and treatment of high-altitude pulmonary edema (HAPE).[57][92]

Primary options

nifedipine: children: consult specialist for guidance on dose; adults: 30 mg orally (extended-release) every 12 hours

HACE only

1st line – descent or simulated descent

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ACUTE
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HACE only
1st line – 

descent or simulated descent

Ideally, those with high-altitude cerebral edema (HACE) should descend quickly to low altitude.

In the event of any delay, the partial pressure of inspired oxygen (PIO2) can be increased by using supplemental oxygen (face mask or nasal prongs 2-4 L/minute), or a portable hyperbaric chamber (2 psi - 13.8 KPa).[7]

A combination of supplemental oxygen and portable hyperbaric treatment can be used in severe cases.[91]

Plus – dexamethasone

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ACUTE
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HACE only
Plus – 

dexamethasone

Treatment recommended for ALL patients in selected patient group

In high-altitude cerebral edema (HACE), dexamethasone often improves the clinical situation and makes evacuation easier.

Although the duration of the treatment is not clear, once a course of dexamethasone has been started this should be continued until the person has reached low altitude.[3][14]

Primary options

dexamethasone: children: 0.15 mg/kg orally every 6 hours, maximum 4 mg/dose; adults: 8 mg orally initially, followed by 4 mg every 6 hours

OR

dexamethasone sodium phosphate: children: 0.15 mg/kg intramuscularly/intravenously every 6 hours, maximum 4 mg/dose; adults: 8 mg intramuscularly/intravenously initially, followed by 4 mg every 6 hours

concurrent HAPE and HACE

1st line – descent or simulated descent

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ACUTE
|
concurrent HAPE and HACE
1st line – 

descent or simulated descent

Those with concurrent high-altitude pulmonary edema (HAPE) and high-altitude cerebral edema (HACE) should descend quickly to low altitude.

In the event of any delay, the partial pressure of inspired oxygen (PIO2) can be increased by using supplemental oxygen (face mask or nasal prongs 2-4 L/minute), or a portable hyperbaric chamber (2 psi - 13.8 KPa).[7]

A combination of supplemental oxygen and portable hyperbaric treatment can be used in severe cases.[91]

Plus – nifedipine + dexamethasone

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ACUTE
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concurrent HAPE and HACE
Plus – 

nifedipine + dexamethasone

Treatment recommended for ALL patients in selected patient group

Patients require treatment with both nifedipine and dexamethasone.

Nifedipine is able to inhibit hypoxic pulmonary vasoconstriction and reduce pulmonary artery pressure.​[3] It can therefore be used in both prophylaxis and treatment of high-altitude pulmonary edema (HAPE).[57][92] Care should be taken to avoid excessively large decreases in systemic pressure as this may decrease cerebral perfusion pressure and cause cerebral ischemia.

In high-altitude cerebral edema (HACE), dexamethasone often improves the clinical situation and makes evacuation easier.

Although the duration of the treatment is not clear, once a course of dexamethasone has been started this should be continued until the person has reached low altitude.[3][14]

Primary options

nifedipine: children: consult specialist for guidance on dose; adults: 30 mg orally (extended-release) every 12 hours

-- AND --

dexamethasone: children: 0.15 mg/kg orally every 6 hours, maximum 4 mg/dose; adults: 8 mg orally initially, followed by 4 mg every 6 hours

or

dexamethasone sodium phosphate: children: 0.15 mg/kg intramuscularly/intravenously every 6 hours, maximum 4 mg/dose; adults: 8 mg intramuscularly/intravenously initially, followed by 4 mg every 6 hours

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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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