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Prolonged QT interval and atypical antipsychotic drugs

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

  • olanzapine and risperidone are associated with an increased risk of stroke in elderly patients when used to treat behavioural symptoms of dementia
  • postural hypotension is common with antipsychotics that block alpha1 adrenoceptors (e.g. clozapine, olanzapine, quetiapine, risperidone, sertindole, zotepine)
    • this adverse effect is most likely to be problematic in older patients, and those with cardiovascular disease or receiving antihypertensive drugs, in whom dose titration should be slow, with careful monitoring of the blood pressure
  • significant prolongation of the QTC interval may occur with zotepine, as well as with sertindole - drugs which lead to QTC prolongation should be avoided where possible in patients with a history of coronary heart disease, cardiac failure or arrhythmia
    • in such patients, any antipsychotic therapy should be given in the lowest effective dose, and serum electrolytes and ECG checked before starting treatment or increasing the dose
    • concomitant therapy with drugs that delay elimination of an antipsychotic, prolong the QTC interval or lower serum potassium concentration should generally be avoided in patients on antipsychotic drugs
    • the ECG should be monitored, and interpreted by an appropriate specialist, in any patient who needs a high dose of antipsychotic or who develops symptoms suggestive of arrhythmia (e.g. palpitations) while on treatment
  • fatal myocarditis (usually in the first 2 months of treatment) and cardiomyopathy (at any time during treatment) are rare serious effects of clozapine
    • patients with a history suggestive of pre-existing heart disease should be assessed by a specialist before starting clozapine


  1. Drug and Therapeutics Bulletin (2004); 42(8):57-60.

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