Clarithromycin-induced QT prolongation in a patient with incidental parathyroidectomy

Acquired long QT syndrome refers to a syndrome similar to the congenital form but caused by exposure to drugs that prolong the duration of the ventricular action potential. By far the most common cause of acquired long QT syndrome is drug induced, with antiarrhythmics being the group of drugs most commonly implicated. Apart from antiarrhythmics, many drugs capable of inducing QT prolongation are noncardiac and are used for relatively benign conditions. We report a case of QT prolongation in a patient with hypocalcemia secondary to hypoparathyroidism who received clarithromycin. The contributions of these factors to the prolonged QT interval are discussed.