Neuroleptic Malignant Syndrome (NMS)

A potentially lethal adverse effect of drugs that impair dopaminergic transmission. Antipsychotics are the leading cause, but NMS can also occur with antiemetics, antidepressants and lithium, or after abrupt cessation of a dopamine agonist.

Clinical tetrad

• Hyperthermia
• Extrapyramidal effects — lead-pipe rigidity, bradykinesia/akinesia, dystonias, abnormal movements/postures, dysphagia, tremor
• Autonomic instability — tachycardia, hypertension, labile BP, diaphoresis, tachypnoea
• CNS effects — drowsiness, confusion, coma, mutism, incontinence

Investigations

Elevated CK, leukocytosis, low serum iron.

Management

NMS is potentially lethal — send to hospital; some patients need ICU admission.

• Discontinue the causative antipsychotic (or dopamine agonist).
• Supportive care: IV fluids for hydration, active cooling, DVT prophylaxis, monitor vital signs.
• Benzodiazepines may help.
• Bromocriptine 2.5 mg PO 8-hourly is sometimes used, though controlled-trial evidence for antidotal therapy is lacking.

Follow-up

• The ongoing need for antipsychotic medication should be reviewed by a psychiatrist.
• ~30% of patients develop NMS again on rechallenge — do not rechallenge with an antipsychotic without specialist input.