The prolongation of the QT interval on electrocardiogram is a rare but known risk of some psychotropic (and other) medications. A prolonged QT interval can increase the risk of Torsades de Pointes, a ventricular arrhythmia that can be fatal. Although not a concern in the pharmacologic treatment of most patients, caution is recommended when prescribing psychotropic meds with patients with serious comorbid medical illness and/or with cardiac illness.
In general, however, individuals on mono-therapies with no comorbid cardiac histories are not at substantial risk of cardiac side effects and, in balance, the value of appropriate treatment of mental health conditions definitively outweigh a non-specific QTc prolongation concern.
When faced with using psychotropic medication for a patient who has a significant cardiac history or medical illness, there are several factors to consider. In addition to some of the antipsychotic and antidepressant medications, a number of antiarrhythmic, antimicrobial and antihistaminic medications can impact QTc intervals. When a patient’s presentation raises concerns, the website www.crediblemeds.org provides a helpful resource allowing a search for the QT prolonging risks of a specific medication.
In ordinary clinical practice, it is thus important to inquire about consider patient risk factors. Combinations of risk factors, and polypharmacy can create cumulative risk. For patients with significant cardiac risk factors, psychiatric medications with known risk to prolong QTc interval should be avoided, and cardiology input should be considered. While there is no absolute QTc interval at which a psychotropic drug should not be used, the risk-benefit of prescribing at a QTc >500ms should be considered carefully.
The American Psychiatric Association recently published a resource document, available on the APA website and cited below. This document provides insight into underlying pharmacology and pathophysiology, how to measure QT and QTc, and can guide medication management.
The following bullets regarding Patient Risk factors are worth noting (Funk et al, 2018):
- Non-modifiable risk factors: Female sex, Advanced age, Congenital long QT syndrome (LQTS), History of drug-induced QTc interval prolongation, History of structural or functional cardiac disease.
- Modifiable risk factors: Concurrent use of > 1 QTc interval prolonging drug, Drug-drug interactions, Drug toxicity, Rapid intravenous infusion of QTc interval prolonging drugs, Severe acute illness, Bradycardia, Starvation, Hepatically-metabolized drugs in patients with hepatic cirrhosis, Inadequate dose adjustment of renally- eliminated drugs in patients with acute kidney injury or chronic kidney disease, Hypokalemia, Hypomagnesemia, or Hypocalcemia.
Funk, M. C., Beach, S. R., Bostwick, J. R., Celano, C. M., Hasnain, M., Pandurangi, A., … Kovacs, R. J. (2018). APA Resource Document Resource Document on QTc Prolongation and Psychotropic Medications. American Psychiatric Association, (June), 1–42.