Pharmacokinetic studies of nifedipine and digoxin co-administration

We have studied the possible interactions between nifedipine and digoxin in 8 healthy subjects in two ways: A. The effect of digoxin (0.25 mg, tablet q. d. for 8 days) on the pharmacokinetics of nifedipine following single-dose (10 mg capsule) administration. Mean values for peak concentration, area under the serum concentration time curve (AUC), total serum clearance and the half-life of elimination of nifedipine did not differ before and concomitantly with digoxin administration. B. The effect of nifedipine (30 mg t.i.d.p.o. for 6 days) on the pharmacokinetics of digoxin following single dose (0.5 mg i.v.) administration. No significant differences were found between the mean values of the half-life of the α and β phases, the AUC and the apparent volume of distribution of digoxin before and comcomitantly with nifedipine administration. However, during the later period, the mean cumulative 96 h urinary excretion of digoxin increased by 18% (p < 0.05) and the renal clearance of digoxin by 26% (p < 0.05). No change was found, however, in the total plasma clearance of digoxin.