Poisoning from - antipsychotics

Description

Overdose of typical (haloperidol, chlorpromazine) or atypical (quetiapine, olanzapine, clozapine) antipsychotics
Quetiapine - most commonly implicated in Australian deliberate self-poisoning presentations, dose-dependent sedation to coma
Dominant risks: CNS depression, QT prolongation/arrhythmia, hypotension, and anticholinergic effects (esp. olanzapine, quetiapine, chlorpromazine)

One of the commonest agents in deliberate self-poisoning presenting to Australian EDs
Often co-ingested with other psychotropics

Dopamine D2 antagonism -> extrapyramidal effects, hyperprolactinaemia (less relevant acutely)
Alpha-1 antagonism -> hypotension
Antimuscarinic effects -> anticholinergic toxidrome features
hERG potassium channel blockade -> QT prolongation -> torsades
CNS depression - can be profound, prolonged (esp. quetiapine XR, large ingestions)

Clinical - depressed conscious state +/- anticholinergic features +/- hypotension
ECG mandatory - QTc, QRS - repeat serially as absorption can be delayed with modified-release preparations
Consider co-ingestants (paracetamol level in all deliberate self-poisoning)

Supportive - airway protection for coma, IV fluids +/- noradrenaline for hypotension (avoid adrenaline - unopposed alpha effect from concurrent alpha-blockade can worsen hypotension)
Continuous cardiac monitoring - correct hypokalaemia/hypomagnesaemia, treat torsades with IV magnesium
Activated charcoal if early and airway protected
Benzodiazepines for extrapyramidal agitation/dystonia; benztropine for acute dystonic reactions
Prolonged observation (12-24h+) for modified-release quetiapine given delayed, prolonged absorption

Neuroleptic malignant syndrome - not typically an acute overdose feature but consider with chronic use + acute deterioration
Seizures - especially with chlorpromazine, clozapine
Clozapine specifically - agranulocytosis (chronic use), myocarditis, severe constipation/ileus

Most recover fully with supportive care over 24-48h
Death rare, but underlies significant morbidity from aspiration and prolonged sedation
QT prolongation risk persists as long as the drug is present - do not stop cardiac monitoring early

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