RESIDENT: Untwisting Antipsychotic Medications and the Risk of QT Prolongation
Dr. Zahinoor IsmailDate and time:
23 Mar 2019 from 13:50 to 14:10Location: Bluebell
- Review the pathophysiology of QT interval prolongation;
- Review pharmacodynamics and pharmacokinetics related to antipsychotic medication and QT prolongation;
- Discuss recommendations for minimizing risk associated with antipsychotic medication and QT prolongation.
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Clinical implications of QT interval prolongation associated with antipsychotic treatment include the risk of fatal arrhythmias and sudden
cardiac death. The QT interval represents the electrocardiographic manifestation of ventricular depolarization and repolarization. The
etiology of QT prolongation is generally divided into congenital (long QT syndrome) and acquired causes. Clinically, most QT
prolongation is acquired, with medications being the most common cause for this. Medication-induced QT prolongation is usually
secondary to blockade of the iKr potassium channel, which can predispose patients to develop life-threatening arrhythmias including
torsades de pointes. Both conventional and atypical antipsychotics can lead to iKr blockade. From a pharmacodynamic perspective,
multiple antipsychotic medications have an additive effect on QT interval. From a pharmacokinetic perspective, decreased clearance of
high risk drugs when co-prescribed with metabolic inhibitors of the pathways responsible for their metabolism can also result in a
prolonged QT interval. Informed clinical decision making, including obtaining an ECG in patients with risk factors, and routine risk-benefit
calculation with consideration of the pharmacodynamics and pharmacokinetics prior to prescribing antipsychotic medications can
minimize the risk of life threatening cardiac complications in treating individuals with psychosis.