Effects of benazepril and hydrochlorothiazide, given alone and in low- and high-dose combinations, on blood pressure in patients with hypertension.

OBJECTIVE: To assess the efficacy and safety of several combinations of benazepril, an angiotensin-converting enzyme inhibitor, and hydrochlorothiazide, as compared with placebo, in the treatment of patients with essential hypertension.

DESIGN: A 6-week, randomized, double-blind, parallel study conducted at 24 centers. A placebo run-in period of 1 to 4 weeks preceded the double-blind phase.

PARTICIPANTS AND SETTING: Male and female outpatients, aged 18 years and older, were eligible to participate if their sitting diastolic blood pressure was between 95 and 114 mm Hg at the last two consecutive visits during the placebo phase. Among the 334 patients who entered the double-blind phase, 17% were aged 65 years or older and 26% were black. Eleven patients withdrew because of adverse experiences, including two patients receiving placebo.

INTERVENTIONS: Patients received placebo; benazepril, 20 mg; hydrochlorothiazide, 25 mg; or combination therapy with benazepril/hydrochlorothiazide, 5/6.25 mg, 10/12.5 mg, 20/25 mg, 20/6.25 mg, or 5/25 mg, once daily for 6 weeks.

MAIN OUTCOME MEASURES: The mean change from baseline in sitting diastolic blood pressure at end point (last postrandomization measurement carried forward) in the double-blind phase. Combination therapy with benazepril/hydrochlorothiazide, 20/25 mg, was compared with benazepril, 20 mg alone, and hydrochlorothiazide, 25 mg alone. Sitting systolic blood pressure and the effect of race and age on treatment efficacy were also evaluated.

RESULTS: Compared with placebo, all benazepril/hydrochlorothiazide combinations produced statistically significant reductions from baseline in sitting diastolic and systolic blood pressures at study end point. In the benazepril/hydrochlorothiazide, 20/25 mg, group, the adjusted mean changes in sitting diastolic blood pressure at end point were statistically significantly greater than those in the monotherapy treatment groups (benazepril, 20 mg, P < or = .05; hydrochlorothiazide, 25 mg, P < or = .001) alone. All therapies were generally well tolerated. Decreases in mean serum potassium level with hydrochlorothiazide monotherapy were reduced or eliminated with combination therapy.

CONCLUSION: Benazepril in combination with hydrochlorothiazide, including a low-dose combination of 5/6.25 mg, is effective in reducing sitting diastolic and systolic blood pressure in patients with hypertension.