Comparison of the antihypertensive effect of imidapril and enalapril in the treatment of mild to moderate essential hypertension: A randomized, double-blind, parallel-group study

Background: Imidapril is a novel angiotensin-converting enzyme (ACE) inhibi tor that has been shown to be effective in the treatment of mild to moderat e hypertension at doses ranging from 5 to 40 mg. Objective: The purpose of this study was to compare the antihypertensive ef ficacy of imidapril (5-10 mg daily) with that of the ACE inhibitor enalapri l (5-10 mg daily) in patients with essential hypertension. Methods: After a 4-week, single-blind, placebo run-in phase, patients were randomized to receive imidapril 5 to 10 mg daily or enalapril 5 to 10 mg da ily for 12 weeks. The dose of medication could be doubled if mean sitting d iastolic blood pressure (DBP) remained > 90 mm Hg after 4 weeks of treatmen t. Response was defined as sitting DBP less than or equal to 90 mm Hg or a reduction in sitting DBP of greater than or equal to 10 mm Hg compared with baseline. Efficacy and safety were evaluated in the intent-to-treat popula tion. Results: A total of 353 patients from 24 centers were randomized to treatme nt (176 imidapril; 177 enalapril); 341 completed the trial. One patient did not receive study medication; the intent-to-treat population therefore con sisted of 352 patients. There was no difference between groups in the propo rtion of patients who responded favorably to treatment with imidapril (131/ 175 [74.9%]) or enalapril (131/177 [74.0%]). Clinically relevant reductions in sitting and standing DBP and systolic blood pressure were apparent afte r 2 weeks of treatment, and there was a trend toward further reductions for the remainder of the study period in both treatment groups. There was no s ignificant difference in the numbers of patients with greater than or equal to1 adverse event between the imidapril group (76/175 [43.4%]) and the ena lapril group (86/177 [48.6%]). In both treatment groups, the most common ad verse events (occurring in >5% of patients) were headache, bronchitis, coug h, and upper respiratory tract infections. There was no difference between groups in the incidence of treatment-related adverse events. Conclusions: The results of this study suggest that imidapril and enalapril are equally effective and well tolerated in patients with mild to moderate essential hypertension. The dose range of 5 to 10 mg for imidapril was app ropriate for the treatment of patients with essential hypertension.