Effects of diltiazem on plasma level and urinary excretion of digoxin in healthy subjects.

To evaluate a possible effect of diltiazem hydrochloride (DTZ) on digoxin (DX) kinetics, we performed a study in which a single oral dose of DX (0.5 or 0.75 mg) was given with and without DTZ (30 mg three times daily for 1 wk) to six healthy subjects. DTZ increased plasma DX concentrations at 3, 4, 6, and 12 hr and decreased renal clearance of DX from 3.05 +/- 0.126 to 2.31 +/- 0.234 ml/min/kg. There was no significant change in absorption t 1/2, peak concentration, peak concentration time, distribution t 1/2, biologic elimination t 1/2, or apparent volume of distribution with DTZ.