Pharmacology & TherapeuticsPending review

Serotonin Syndrome

Excess stimulation of central and peripheral serotonin receptors from serotonergic drug combinations produces a rapid-onset triad of neuromuscular, autonomic and mental-state disturbance that resolves once the receptor drive is removed or blocked.

In a nutshell

Serotonergic drug combinations flood central and peripheral 5-HT receptors, producing a rapid-onset triad of neuromuscular hyperactivity, autonomic instability and altered mental state. It is distinguished from neuroleptic malignant syndrome by its opposite mechanism (serotonin excess versus dopamine blockade), faster onset and clonus rather than lead-pipe rigidity.

Classic presentation

A patient recently started on, or with a dose increase of, a serotonergic drug (or combination, especially involving an MAOI) presenting within hours with agitation, clonus, hyperreflexia, tremor, hyperthermia and diarrhoea.

Key points

Clonus is the single most discriminating sign on examination.

You’ve reached the end of the preview

This topic is part of full high-yield access. Create a free account to read every key point, first-line investigation and exam trap — or browse the free sample topics without one.

Educational content pending clinical review. Not medical advice.