Differentials
Cocaine overdose
SIGNS / SYMPTOMS
Toxicity from amfetamines cannot be readily distinguished clinically from cocaine toxicity, but the management in both cases is essentially the same. The prevalence of ischaemic chest pain and stroke in cocaine intoxication is higher.
INVESTIGATIONS
Urine drug screen will differentiate cocaine from amfetamines.
Serotonin syndrome
SIGNS / SYMPTOMS
History of drug use, prescription or illicit, with proclivity to serotonin interaction (e.g., serotonin-reuptake inhibitors, metoclopramide, sumatriptan, lithium, and dextromethorphan). Anxiety, agitation, delirium, restlessness, and disorientation; bilateral Babinski's signs; neuromuscular findings are typically more pronounced in the lower extremities.
INVESTIGATIONS
Non-specific laboratory findings, including an elevated WBC count, elevated creatine kinase, and decreased serum bicarbonate concentration. Level for suspected agent causing interaction (if available) may be diagnostic.
Psychosis
SIGNS / SYMPTOMS
May be drug-induced or exacerbation of pre-existing condition and difficult to discern exactly, but differentiating these is not a contra-indication to urgent sedation and symptomatic therapy.
INVESTIGATIONS
A period of sedation and behavioural control followed by a more extensive history will allow reassessment after the acute drug effects have worn off.
Alcohol use disorder
SIGNS / SYMPTOMS
Commonplace, chronic in nature, malnutrition, hepatomegaly, jaundice, and ascites.
INVESTIGATIONS
Carbohydrate-deficient transferrin confirms diagnosis but is not widely available. Serum alcohol >22,440 micromol/L (200 mg/dL) with limited impairment can indicate tolerance to the effects of alcohol but does not diagnose dependence.
Hypoglycaemia
SIGNS / SYMPTOMS
History of diabetes mellitus and insulin therapy, or oral hypoglycaemic agents.
INVESTIGATIONS
Documentation of blood glucose <3.3 mmol/L (60 mg/dL) with accompanying symptoms is crucial to diagnosing clinically significant hypoglycaemia.
Sedative or hypnotic withdrawal
SIGNS / SYMPTOMS
History of prolonged use or high doses, discontinued in the previous 1 to 6 days. Hyperthermia is not a prominent feature. Older people are more at risk. Usually a longer period of onset.
INVESTIGATIONS
Toxicology screening may identify the agent.
Antimuscarinic syndrome
SIGNS / SYMPTOMS
Rather than the diaphoresis of sympathomimetic toxicity, a patient with antimuscarinic syndrome has dry mucosal membranes and hot, red, and dry skin. Older men are likely to have urinary retention. Voluntary admission of ingestion of anticholinergic agents, antihistamines, antispasmodic agents, some antidepressants (especially tricyclic antidepressants), ophthalmic cycloplegics, or some plant derivatives including belladonna and Datura species.
INVESTIGATIONS
Toxicology screening may identify the agent.
Alcohol withdrawal
SIGNS / SYMPTOMS
History of chronically high alcohol intake followed by abrupt withdrawal may be elicited. Hypertension, tachycardia, and agitation become more severe within hours to several days.
INVESTIGATIONS
A clinical diagnosis.
Heat stroke
SIGNS / SYMPTOMS
History of exposure to extreme heat, especially with physical exertion; hot, flushed, and dry skin; variable amounts of sweating may occur, but usually less than expected with amfetamine toxicity. Prostration, exhaustion are much more common than agitation and rage.
INVESTIGATIONS
Concentrated urine, haemoconcentration with decreased coagulation, and thrombocytopenia. Elevated WBC count and core body temperature, usually negative drug and alcohol screens.
Subarachnoid haemorrhage
SIGNS / SYMPTOMS
Sudden severe (thunderclap) headache, often described as the worst headache of life, with nausea, vomiting, and photophobia, meningismus, intra-ocular haemorrhages, or focal findings.
INVESTIGATIONS
Subarachnoid haemorrhage identifiable on CT head (non-contrast). Lumbar puncture with blood may indicate cerebral bleeding or traumatic spinal tap. Cerebral angiography confirms the presence of aneurysms.
Phaeochromocytoma
SIGNS / SYMPTOMS
History of similar attacks with headache in the absence of drug misuse.
INVESTIGATIONS
Urinary catecholamines are elevated, or elevated metanephrines, with normal serum T4.
Thyrotoxic crisis
SIGNS / SYMPTOMS
History of thyrotoxicosis in the past, may be precipitated by amfetamine or other sympathomimetic ingestion.
INVESTIGATIONS
Elevated levels of T3, T4 and free thyroxine, hyperglycaemia, leukocytosis, and anaemia.
Encephalitis
SIGNS / SYMPTOMS
Fever, headache, lethargy, and altered mental status; immunocompromised state, motor and sensory deficits, or focal neurological findings; seizures.
INVESTIGATIONS
CT head (non-contrast) normal or subtly abnormal, hypodense lesions, and mild mass effect prominent later; lumbar puncture for cerebrospinal fluid (cell count and culture), bloods for bacterial culture diagnostic with identification of organism.
Meningitis
SIGNS / SYMPTOMS
Headache, lethargy, and altered mental status; immunocompromised state, fever, meningismus, and lethargy, seizures.
INVESTIGATIONS
CT head (non-contrast) normal; lumbar puncture for cerebrospinal fluid (Gram stain), bloods for bacterial culture diagnostic with identification and recovery of organism.
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