prolonged QT interval and thioridazine

Last reviewed 01/2018

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.