Doctors are advised to switch patients to other antipsychotic drugs.
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 year 2000, HSA has strengthened the package inserts of all registered brands of thioridazine to warn of these adverse effects.
Early this year, Novartis, the manufacturer of the proprietary brand of thioridazine, Melleril®, announced the worldwide voluntary withdrawal of all forms of Melleril® by 30 June 2005 because its risk-benefit balance no longer met current clinical and regulatory expectations. Although Melleril® is not marketed in Singapore, there are 4 generic brands of thioridazine that are currently registered in Singapore: Aldazine® (Merck), Apo-thioridazine® (Pharmaforte), Merpazine® (Duopharma) and Melibon® (Kyowa Hakko).
HSA's follow up action
Following Novartis' decision to withdraw its products, 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 from available data, the PVAC arrived at an unfavorable risk-benefit outcome for the drug in view of the risk of serious cardiac arrhythmias and the availability of alternative antipsychotic treatments. Hence, HSA will deregister the generic brands of thioridazine with effect on 31 March 2006.
