Acute poisoning with thioridazine

Objective: As previous single case reports have indicated that acute poisoning with thioridazine can be potentially dangerous, an investigation was undertaken to find out whether the risk of severe poisoning in adults and children can be judged from the amount of the drug that has been taken. Patients and methods: In a case-control study 202 medical notes of 202 patients were analysed (141 adults, aged 16-82 years; 61 children, aged 0,3 - 15 years) in which thioridazine was the only potentially harmful substance taken, the precise amount swallowed was known and the drug was the certain or probable cause of the signs. 30 children were excluded from the study, because their body weight was not known. Results: Mild thioridazine poisoning was characterized by somnolence, tremor, ataxia and dysarthria. The severity of the poisoning and the degree of disorder of consciousness correlated significantly with the amount of thioridazine taken. Severe intoxication with coma and ventricular arrhythmias was observed at a dose of 2 g and more. While the disorder of consciousness completely regressed in the first 24 hours, in a few of the patients the cardiac arrhythmias persisted for up to 28 hours after the drug intake. Charcoal administration seemed to influence the course favourably. Conclusion: Prolonged, intensive care supervision and treatment are essential if more than 2 g thioridazine have been swallowed. In addition to standard treatment with gastric lavage charcoal should be given as early as possible to limit absorption.