Rapid death resulting from mesoridazine overdose

A 23-year-old mentally retarded woman was brought to the emergency department 2-2.5 hr after ingesting an unknown quantity of mesoridazine. She was lethargic and somewhat uncooperative, but did answer questions. Her ECG was normal. She was treated with gastric lavage, 50 g activated charcoal, and 10 oz magnesium citrate solution. Her condition continued to decline until, at 2 hr after arrival, she was comatose and becoming increasingly hypotensive. Her ECG showed long runs of markedly widened QRS complexes. The patient was given an iv infusion of dobutamine to maintain blood pressure. She suffered a convulsion, loss of blood pressure, and developed ventricular tachycardia which progressed to ventricular fibrillation unresponsive to electrical cardioversion, pacing, and vigorous prolonged CPR. She was pronounced dead 6-6.5 hr after the ingestion. Antemortem blood level of mesoridazine was 16 micrograms/ml and no other drugs were detected. While sudden deaths have been reported with therapeutic doses of mesoridazine and its parent thioridazine, deaths are uncommon in overdose. Rapid death seen in this case emphasizes the importance of close monitoring and aggressive treatment of phenothiazine overdoses.