Letters to the Editor: QT interval prolongation due to metronidazole administration

The drug induced Q-T prolongation might lead to torsades de pointes (TdP), ventricular tachycardia and sudden cardiac death. Several antimicrobial agents, such as erythromycin, clarithromycin, fluoroquinolones, halofantrine and pentamidine can cause QT prolongation. Metronidazole is a widely used antimicrobial agent and the effect of this drug on QT interval is not well documented (1). A 71-year-old female patient was admitted to emergency unit with severe dyspnea, angina, and orthopnea symptoms in the preceding 5 days. She was on treatment for chronic obstructive lung disease, diabetes mellitus, hypertension and coronary artery disease. She also had a history of drug-induced QT prolongation associated with moxifloxacin. Electrocardiogram (ECG) on admission showed atrial fibrillation with a ventricular rate of 82 /minute. The corrected Q-T interval was 396 msec (Fig. 1). She was treated with diuretics, angiotensin converting enzyme inhibitors, omeprazole and bronchodilators. On follow up diagnosis of nosocomial pneumonia was made and intravenous metronidazole was initiated. Two days after the initiation of antimicrobial therapy, the QT interval prolonged (corrected Q-T interval, 559 msec) and the T waves were inverted (Fig. 2). Laboratory tests, including serum potassium and magnesium levels, were within normal limits. Metronidazole was immediately stopped and the ECG of the patient returned to normal within 48- hours.