Effects of amlodipine on steady-state digoxin concentrations and renal digoxin clearance

The effect of oral amlodipine on steady-state digoxin concentrations and renal clearance was studied in 21 healthy male subjects. After 2-week digitalization (digoxin, 0.375 mg/day), they were randomized in a single-blind crossover protocol to receive either placebo or amlodipine (5 mg/day) in combination with digoxin for the following two 2-week periods. Mean (+/- SD) digoxin concentrations of 0.64 +/- 0.19 ng/ml after 2-week digoxin monotherapy and 0.61 +/- 0.23 ng/ml during placebo were not altered by amlodipine (0.60 +/- 0.18 mg/ml). Renal digoxin clearance was 202 +/- 44 ml/min on placebo and 207 +/- 55 ml/min during amlodipine coadministration. No change in pharmacologic effect of digoxin was noted during amlodipine coadministration, nor was blood pressure or heart rate changed. These data indicate that oral amlodipine does not significantly influence steady-state digoxin concentrations in healthy subjects.