Singapore - Thioridazine, a phenothiazine antipsychotic agent, is known to be associated with an increased risk of QT prolongation, cardiac arrhythmias and sudden death. Following emerging evidence of these safety concerns since 2000, the Health Sciences Agency (HSA) has strengthened the package inserts of all registered brands of thioridazine to warn of adverse effects.

Early this year, the manufacturer of the proprietary brand of thioridazine, Melleril®, announced worldwide voluntary withdrawal by 30 June 2005 because the risk-benefit balance no longer met current clinical and regulatory expectations. Although Melleril® is not marketed in Singapore, there are 4 generic brands currently registered: Aldazine®, Apo-thioridazine®, Merpazine® and Melibon®.

HSA sought the advice of its Pharmacovigilance Advisory Committee (PVAC) and local experts in the field of psychiatry on the balance of risks and benefits of thioridazine. Based on the evidence available, the PVAC arrived at an unfavourable risk-benefit outcome for the drug in view of the possibility of serious cardiac arrhythmias and the availability of alternative antipsychotic treatments. Hence, HSA will deregister the generic brands of thioridazine with effect 31 March 2006.

Reference: Product Safety Alert, 31 March 2005. http://www.hsa.gov.sg/cda/safetyalerts