Discontinuation of thioridazine in patients with learning disabilities: balancing cardiovascular toxicity with adverse consequences of changing drugs

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Abstract
History In December 2000 the Committee on Safety of Medicines restricted the licensed indications for thioridazine. 1 2 This followed publication of data by Reilly et al,3 supported by earlier evidence.4 Psychiatric patients taking thioridazine and droperidol had significantly more prolonged QTc intervals (a marker for risk of ventricular arrhythmias and sudden death) than a healthy population.3 Although Reilly et al emphasised that QTc prolongation is only a surrogate endpoint for risk of ventricular arrhythmias and sudden death, the Committee on Safety of Medicines deemed that the risk was sufficient to limit the use of thioridazine to patients with a diagnosis of schizophrenia and then only as a second line drug. They also introduced a requirement for regular QTc monitoring for patients treated with thioridazine and made concomitant use of thioridazine and other drugs known to cause QTc prolongation a contraindication. 1 2 These changes in the licensed indication for thioridazine not only affect patients requiring antipsychotic drugs for the first time but have also forced doctors to review the use of thioridazine in patients taking the drug for long term prophylaxis.