Dose finding studies with imidapril--a new ACE inhibitor

1. We describe an approach involving a smaller, shorter study, leading onto a longer, larger study in which the antihypertensive effects of ascending doses of imidapril, a new ACE inhibitor, were investigated. Both studies were planned prospectively, assuming a clinically useful fall in BP to be 8 mm Hg (s.d. = 9). The studies included patients with mild to moderate essential hypertension (baseline sitting diastolic blood pressure (SDBP) 95-115 mm Hg). After a placebo run-in of 2-3 weeks patients received either placebo or imidapril 2.5, 5, 10 or 20 mg in the 2 week study (n = 91) or imidapril 5, 10, 20 or 40 mg in the 4 week study (n = 162). 2. The overall mean baseline SDBP was 103.4 mm Hg (s.d. 0.62) in the initial study and 101.5 mm Hg (s.d. 0.41) in the 4 week study. 3. Compared with placebo, imidapril 10, 20 and 40 mg significantly reduced SDBP. There was no significant difference between these doses, suggesting that 10 mg achieved maximal ACE inhibition in most patients. The 2.5 mg dose showed no significant effect. The 5 mg dose gave an intermediate effect. In both studies the overall incidence of adverse events was similar in the imidapril and placebo groups, and was not worrying.