Table 1

 Characteristics of serotonin syndrome and neuroleptic malignant syndrome

Serotonin syndromeNeuroleptic malignant syndrome
CK, creatine kinase; DIC, disseminated intravascular coagulation; 5-HT, 5-hydroxytryptamine (serotonin); MAOIs, monoamine oxidase inhibitors; SSRIs, selective serotonin reuptake inhibitors; TCAs, tricyclic antidepressants; WCC, white cell count.
• Causative drugsSSRIs, TCAs, MAOIsNeuroleptics, metoclopramide, amoxapine (a TCA), sudden dopaminergic drug withdrawal
• Mechanism5-HT receptor overstimulationD2 receptor blockade
• Onset of symptomsWithin 24 hoursWithin 7 days (longer with depot drugs)
• SymptomsAutonomic, mental, neurologicalAutonomic, mental, neurological
• Differentiating symptomsMyoclonus, diarrhoea, nausea, shiveringDysphagia, hypersalivation, incontinence
• SignsDilated pupils, myoclonus, hyperreflexiaTemp >38°C, akinesia, extrapyramidal rigidity
• Laboratory results↑WCC, ↑CK↑WCC, ↑↑CK
• Disease severityWide spectrum mild to severeMore severe—most cases require intensive care
• Serious complicationsDIC, leucopenia, thromboytopenia, seizures, multi-organ failure, rhabdomyolysisDIC, acute renal failure, rhabdomyolysis, myocardial infarction, sepsis, cerebellar neuronal degeneration
• Main treatmentDiscontinue causative drug(s); supportiveDiscontinue causative drug(s); supportive
• Specific treatmentsBenzodiazepines, cyproheptadine, chlorpromazineDopamine agonists, amantadine, carbidopa–levodopa, dantrolene
• Recovery70% within 24 hours2–14 days
• MortalityTotal of 23 deaths reported up to 199910–20% of cases