Sections View Full Chapter Figures Tables Videos Annotate Full Chapter Figures Tables Videos Supplementary Content + Download Section PDF Listen ++ For further information, see CMDT Part 38-21: Antipsychotic Drug Overdose + Key Features Download Section PDF Listen +++ ++ Conventional antipsychotics act mainly on CNS dopamine receptors; examples include Chlorpromazine Haloperidol Droperidol Newer "atypical" antipsychotics also interact with serotonin receptors; examples include Risperidone Olanzapine Ziprasidone Quetiapine Aripiprazole + Clinical Findings Download Section PDF Listen +++ ++ Drowsiness, orthostatic hypotension, especially with α-blocking agents Large overdose Miosis Severe hypotension Tachycardia Convulsions Obtundation or coma Prolongation of QRS interval (thioridazine) or QT interval (with possible torsades de pointes) An acute extrapyramidal dystonic reaction may occur with therapeutic or toxic doses Spasmodic contractions of the face and neck muscles, extensor rigidity of the back muscles, carpopedal spasm, and motor restlessness More common with butyrophenones, less common with atypical drugs Severe rigidity, hyperthermia, and metabolic acidosis (neuroleptic malignant syndrome) may occasionally occur and are life-threatening Atypical antipsychotics have also been associated with weight gain and diabetes mellitus, including diabetic ketoacidosis + Diagnosis Download Section PDF Listen +++ ++ Largely based on history of exposure Most agents are not detected in routine rapid toxicology screens Serum levels are not helpful ECG monitoring for QRS, QT prolongation + Treatment Download Section PDF Listen +++ ++ Activated charcoal Give 60–100 g (in aqueous slurry) orally or via gastric tube Do not use for comatose or convulsing patients unless they are intubated with a cuffed endotracheal tube Widened QRS interval Seen in thioridazine poisoning May respond to intravenous NaHCO3 as used for tricyclic antidepressants Hypotension often responds to intravenous saline boluses; cardiac arrhythmias associated with widened QRS intervals on the ECG may respond to intravenous sodium bicarbonate as is given for tricyclic antidepressant overdoses Prolonged QT interval or torsades de pointes, or both Magnesium 1–2 g intravenously Consider overdrive pacing Treat hyperthermia, maintain cardiac monitoring For extrapyramidal signs Diphenhydramine, 0.5–1.0 mg/kg intravenously, or benztropine mesylate, 0.01–0.02 mg/kg intramuscularly Continue with oral doses for 1–2 days Bromocriptine (2.5–7.5 mg daily orally) may be effective for mild or moderate neuroleptic malignant syndrome Dantrolene (2–5 mg/kg intravenously) has also been used for muscle contractions but is not a true antidote