Kiran N, Azam S, Dhakam S.
Clarithromycin induced Digoxin Toxicity: Case Report and review.
J Pak Med Assoc Jan ;54(8):440-1.

A 56 year-old woman with history of severe rheumatic mitral stenosis and atrial fibrillation, was being treated with digoxin 0.25mg and warfarin 3mg daily for the past five years. Patient`s target international normalized ratio (INR) was being maintained between 2.0 and 3.0. She presented to our institution with fever and cough for 5 days. Two days prior to presentation, she was started empirically on clarithromycin 500 mg twice daily by her primary care physician for presumed community acquired pneumonia. Her chest X-ray on admission was abnormal for left lower lobe pneumonia. Patient was started on intravenous ampicillin/clavulanic acid 1.2 gm every eight hours and clarithromycin was also continued. Initial electrocardiogram (EKG) showed atrial fibrillation with ventricular rate of 70/minute with minor lateral T wave abnormalities. Two days later patient developed profound weakness associated with nausea, vomiting, dizziness and dyspnea. On examination pulse rate was 40/minute. Another 12 lead EKG done showed underlying atrial fibrillation with complete heart block, junctional escape rhythm and multifocal PVCs with fixed coupling interval. Laboratory results revealed digoxin level of 8.7 ng/ml (therapeautic range=l.0-2.6) and an international normalized ratio (INR) of 3.97 (2.0-3.0). Due to nonavailability of digoxin binding fragments only a temporary pacemaker was inserted to increase the heart rate. Her heart rhythm returned to baseline (atrial fibrillation) after 48 hours with decrease in digoxin level to 3.0 ng/ml. The patient was finally discharged on day 7 with a digoxin level 1.6 ng/ml and a plan to undergo mitral valve replacement.

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