The effects of captopril on serum digoxin levels in patients with severe congestive heart failure

The effects of captopril on serum digoxin concentrations were studied in 8 patients with severe (NYHA Class IV) congestive heart failure. Serum digoxin concentrations were determined before and after the administration of captopril for 1 week in patients on chronic digoxin therapy, Each patient who was taking 0.25 mg of digoxin PO q.d., was administered 12.5 mg of captopril PO t.i.d. for 7 days. The peak serum concentration of digoxin (C-max) before and after (on Days 0 and 7) captopril administration was 1.7 +/- 0.2 ng/ml and 2.7 +/- 0.2 ng/ml, the time to peak (t(max)) was 2.4 +/- 0.5 h and 1.3 +/- 0.2 h, and the area under the 24-hour digoxin concentration-time curve (AUC(0-24h)) was 30.0 +/- 1.5 ngxh/ml and 41.7 +/- 3.4 ngxh/ml, respectively. While captopril caused a significant increase in peak serum concentration and the area under the digoxin concentration-time curve, it decreased the time to digoxin peak (p = 0.01, p = 0.04, p = 0.01, respectively). No patient developed evidence of digoxin toxicity. Concomitant administration of captopril with digoxin increases serum digoxin concentration in patients with severe congestive heart failure.