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Prolonged QT interval and thioridazine

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

The Committee on Safety of Medicines (CSM) has advised that the use of thioridazine should be restricted to the second line treatment of schizophrenia in adults:

  • this is after the CSM considered the evidence relating to the rare but serious cardiotoxicity (QTc interval prolongation and ventricular arrhythmias)
  • the balance of risks and benefits is unfavourable for its previous indications (agitation and restlessness in the elderly, anxiety, violent and dangerously impulsive behaviour, mania/hypomania, and behavioural disorders and epilepsy in children)
  • thioridazine treatment should be supervised by a consultant

The CSM advice notes that clinicians should re-evaluate their patients treated with thioridazine, in light of the new evidence. If thioridazine is discontinued then a gradual reduction in dose over one or two weeks is recommended.

The summary of product characteristics should be consulted before prescribing this drug.


  • (1) Message from Professor Alasdair Breckenridge, Chairman, Committee on Safety of Medicines, Thioridazine: restricted indications and new warnings on cardiotoxicity, 11/12/00.

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