This 12-week, multicentre, double-blind, placebo-controlled, parallel-group study compared efficacy of the angiotensin-converting enzyme (ACE) inhibitor imidapril 5 - 10 mg/day and the calcium channel blocker nifedipine slow-release (SR) formulation 20 - 40 mg twice daily. In total 320 patients aged 18 - 75 years, with mean sitting diastolic blood pressures of 95 - 115 mmHg, were randomized to treatment with imidapril (n = 157) or nifedipine SR (n = 163). Efficacy evaluations were based on the intent-to-treat principle. On study completion, there was no difference between the groups with respect to the primary efficacy variable of response to treatment (imidapril 63.1%; nifedipine SR 61.3%). After 2 weeks' treatment, clinically relevant decreases in blood pressure were observed in both groups, with a trend towards further reductions until study end. Fewer patients in the imidapril-treated group than the nifedipine group withdrew due to adverse events that occurred on treatment with study medication (3.2% versus 16.0%) or experienced adverse events (40.1% versus 49.7%). In addition, fewer adverse events were causally related to imidapril (24.2%) compared with nifedipine SR (41.7%). These results show that imidapril is effective in the treatment of essential hypertension and is better tolerated than nifedipine SR.

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