The pharmacodynamics and dose-response relationships of the angiotensin converting enzyme inhibitor, cilazapril, in essential hypertension.

In a double-blind, placebo controlled, crossover study 12 patients with essential hypertension received single doses of 5, 10 and 20 mg of cilazapril, a new angiotensin converting enzyme (ACE) inhibitor. All doses similarly and significantly (P less than 0.05) reduced supine and erect blood pressure without increasing heart rate. The hypotensive effect was evident within 1 h, maintained for up to 8 h, with a maximal effect at 6 h. There was no discernible effect on blood pressure at 24 h after dosing. Plasma ACE activity was markedly inhibited to the same extent after all doses, with a peak inhibition of 94-96% at 2-3 h. At 24 h residual inhibition of ACE was 49-54%. Plasma renin activity increased in a dose-dependent manner with a peak at 6 h, and returned to baseline at 24 h. No correlation was found between the reduction in blood pressure and plasma renin activity, either at baseline or following cilazapril. There were no significant changes in plasma noradrenaline and the responses to upright posture and to dynamic exercise were preserved. There was no evidence of impaired exercise performance. Cilazapril is a potent ACE inhibitor with a rapid onset and a prolonged duration of action. These results suggest that peak ACE inhibition is achieved by 5 mg and that lower doses may be useful in clinical practice.