Quinapril has been extensively studied for efficacy and safety in patients with hypertension or congestive heart failure (CHF) in the United States and Europe. Thirty-nine clinical pharmacology studies involving 383 patients have been completed. Moreover, 12 controlled, multicenter clinical studies and 3 single-center studies involving 1,793 patients have been conducted in hypertension. Three hemodynamic trials, two of which included both acute and long-term phases, and one placebo-controlled, dose-response study have been conducted in 333 patients with CHF. An additional 519 patients who completed studies on comparative agents were started on quinapril at the initiation of six long-term, open-label trials, which extended for up to 3 years. Twelve of 15 hypertension trials evaluated quinapril as first-line monotherapy in 1,452 patients with hypertension. Comparative agents included placebo in five trials (524 patients), enalapril in three trials (339 patients), captopril in four trials (335 patients), and chlorthalidone in one trial (74 patients). A total of 510 patients received quinapril in addition to a diuretic in double-blind trials: 341 patients with moderate to severe hypertension participated in three trials, and 169 patients with CHF participated in one trial. Quinapril administered once daily (o.d.) was evaluated in four placebo-controlled studies and in two studies of o.d. vs. twice-daily doses. The safety of quinapril has been evaluated in almost 2,700 patients in controlled, double-blind studies or in open-label extensions, for a total of more than 1,600 patient-years of exposure to quinapril. More than one-half of all patients participated in long-term trials: 980 patients were studied for 1 year and 315 patients were studied for 2 years at the time of data analysis. Safety data are available for 451 older patients (aged ≥ 65 years), and comparative safety data from other compounds in the controlled studies are available for 1,058 patients. Quinapril's efficacy is comparable to that of other angiotensin-converting enzyme (ACE) inhibitors, and it has a lower incidence of adverse events or withdrawals due to adverse events than has been associated with captopril or enalapril.
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