Clinical presentation

Clinical effects of immediate-release antipsychotic drug ingestions usually appear within 6 hours. After ingesting a modified-release preparation (eg paliperidone), toxicity may be delayed for up to 12 hours.

Effects of antipsychotic drug poisoning include:

• central nervous system (CNS) effects
  • CNS depression (altered conscious state ranging from drowsiness to coma)
  • miosis, respiratory depression
  • extrapyramidal effects—acute dystonias, parkinsonism, tardive dyskinesia; these effects are uncommon, but occur more often with haloperidol and risperidone poisonings, and antipsychotic drug poisonings in children
• cardiovascular effects
  • tachycardia, hypotension due to peripheral vasodilation from alpha-receptor blockade (with larger ingestions), arrhythmias
  • QT-interval prolongation—reported for some antipsychotic drugs (eg amisulpride, ziprasidone, haloperidol); amisulpride and ziprasidone can cause QT-interval prolongation even at therapeutic doses
• anticholinergic effects—dry mouth, mydriasis, constipation, urinary retention, anticholinergic delirium
• gastrointestinal effects—hypersalivation (clozapine), vomiting (lurasidone).

All antipsychotic drugs have been associated with neuroleptic malignant syndrome, which can occur at therapeutic doses. Although this syndrome is rare, it is potentially life threatening. Early supportive care is key to a good outcome.