Prolonged toxicity after massive olanzapine overdose: two cases with confirmatory laboratory data.

Olanzapine is a second-generation atypical antipsychotic that is increasingly used in preference to older antipsychotic agents. Limited data is available concerning the toxic effects of olanzapine after deliberate overdose. Two patients presented to our institution after massive olanzapine ingestion, and required prolonged ventilatory support due to the development of coma and respiratory depression. Serum olanzapine concentrations were orders of magnitude higher than those associated with therapeutic doses, and remained elevated for several days after ingestion. Both patients made a full recovery with only supportive care, despite having initial serum drug concentrations > 2500 microg/l. These reports indicate the potential for olanzapine ingestion to cause coma that may persist for several days after overdose.