Quinapril, when given as initial monotherapy or in addition to diuretics, was extensively evaluated in patients with moderate to severe hypertension, defined as sitting diastolic blood pressure (DBP) ≥ 105 mm Hg with concomitant diuretic therapy or ≥ 110 mm Hg during placebo baseline. In four double-blind, comparative trials and a subset analysis from a placebo-controlled study, 368 patients were treated with quinapril, and 338 patients were treated with comparative therapies (i.e., captopril, enalapril, or placebo). In three studies, quinapril was given in addition to diuretics, and in one study nonresponders received optional atenolol. Two studies assessed quinapril as first-line monotherapy, with nonresponders receiving hydrochlorothiazide in one study. Quinapril dosages ranged from 10 to 40 mg/day, with some patients receiving up to 80 mg/day. Quinapril effectively reduced blood pressure in patients with moderate to severe hypertension either as first-line monotherapy or when given concomitantly with a diuretic or a β-blocker. Quinapril was comparable in efficacy to enalapril, and in several analyses quinapril was significantly more efficacious than captopril (p < 0.05). Quinapril was well tolerated, and the incidence of adverse events was comparable with or less than that of captopril or enalapril.
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