INTERACTION BETWEEN DIGOXIN AND THE CALCIUM-ANTAGONISTS NICARDIPINE AND TIAPAMIL

  • 1 January 1983
    • journal article
    • research article
    • Vol. 5  (6) , 595-602
Abstract
Whether nicardipine and tiapamil interact with digoxin [used to treat atrial fibrillation or congestive heart failure], resulting in increased plasma digoxin levels was tested. Ten patients (mean age, 67 yr) taking 0.13-0.25 mg of digoxin daily were given nicardipine (20 mg TID [3 times a day]), and 8 patients (mean age, 77 yr) taking 0.13-0.25 mg of digoxin daily were given tiapamil (200 mg TID). Plasma levels of digoxin and nicardipine, heart rate, blood pressure, weight, serum electrolytes and serum enzymes were measured and the ECG was monitored twice before, 4 times during and once after the intervention with a Ca antagonist. No measurments of plasma levels of tiapamil were made. A chest roentgenogram was taken before, during and after use of nicardipine or tiapamil. Mean plasma digoxin levels increased significantly in patients reveiving nicardipine (P < 0.05) and in patients receivng tiapamil (P < 0.01), but the values returned to normal after treatment with the experimental drug was discontinued. A wide variation of plasma nicardipine levels was observed, but there was no proportionate correlation between these levels and changes in digoxin levels. Blood pressure decreased significantly (P < 0.01) and heart rate increased significantly (P < 0.05) in patients receiving nicardipine. Similar changes in blood pressure and heart rate were not seen in patients receiving tiapamil. Although the use of each Ca antagonist led to an increase in plasma digoxin levels, the effect of tiapamil was greater than that of nicardipine.

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