Background: In the treatment of hypertension, combination therapy is im- portant because antihypertensive monotherapy is effective in only 40% of pa- tients worldwide. Amlodipine is a dihydropyridine calcium channel blocker with a slow onset and long duration of action. Benazepril hydrochloride is a prodrug hydrolyzed by esterase to the active metabolite benazeprilat, an angiotensin- converting enzyme inhibitor. In 1995, the US Food and Drug Administration ap- proved the use of a capsule formulation of combination amlodipine-benazepril for hypertension. Objective: The aim of this study was to compare the bioavailability and tol- erability of the capsule formulation with those of a tablet formulation of combi- nation amlodipine-benazepril in healthy volunteers. Methods: This single-dose, 2-sequence, 2-period, open-label, crossover study recruited healthy, adult, male volunteers with normotension. Subjects were randomly assigned to 1 of 2 treatment sequences: a single-dose tablet con- taining amlodipine 5 mg plus benazepril 10 mg, followed by a single-dose cap- sule containing the same dose of each drug (AB), or vice versa (BA). The treat- ment period for each drug consisted of dosing and pharmacokinetic analysis on day 1, followed by pharmacokinetic analysis on days 2 to 7. Treatment periods were separated by a 4-week washout period. For pharmacokinetic analysis, serial blood samples were obtained before dosing and at 20, 40, 60, 80, and 100 minutes and 2, 3, 4, 5, 6, 7, 8, 10, 12, 24, 36, 60, 84, 108, 132, and 156 hours after dosing. Tolerability was assessed using subject interview and spontaneous reporting. Results: Twelve healthy, male, Taiwanese subjects (mean (SD) age, 23.5 (1.7) years) participated in the study. No statistically significant differences in bioavailability were found between the 2 formulations based on the pharmaco- kinetic measurements of amlodipine and benazeprilat. The rate and extent of