Several medications, including drugs prescribed for non-cardiac indications, have been associated with a prolongation of the QT interval on the ECG. Under certain circumstances, including patients with congenital LQTS, these drugs will excessively prolong the QT interval, triggering polymorphic ventricular tachycardia. Drugs that prolong the QT interval belong to several pharmacological classes, but most of them share one pharmacological effect: they lengthen cardiac repolarization, primarily by blocking specific cardiac K (Potassium) channels. The potent blocking of cardiac K channels and excessive lengthening of cardiac repolarization leads to prolonged QT intervals.
Patients with QT prolongation on ECG or a genetic predisposition to LQTS should avoid QT prolonging drugs. These drugs will prolong QT even in a normal person. They include drugs available on prescription and those that may be purchased over the counter.
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Margaret has been taking trimethoprin, as prescribed, for chronic urinary tract infections. Trimethorpin is known to prolong the QT interval. This is discontinued on admission to hospital.
Take a look at CredibleMeds for drugs to be avoided.
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A list of drugs that prolong QT and/or cause Torsades de Pointes can be found at:
This is a very useful resource which remains current when the list of those drugs to be avoided changes.
