Different effects of two angiotensin converting enzyme inhibitors in primary hypertension--a comparison of captopril and enalapril.

A comparison of the antihypertensive effect and tolerability of captopril and enalapril was performed. Forty patients with primary hypertension were treated in randomized order, investigated immediately and in a crossover trial with treatment for 6 weeks, with an intermediate placebo wash-out of 3 weeks. A plasma renin profile was obtained from each patient before treatment. The immediate maximal mean change in supine blood pressure (BP) was similar with both drugs, but occurred earlier with captopril. After 6 weeks of treatment enalapril was more potent than captopril in the mean reduction of supine BP produced. This was even more evident in patients with low-renin hypertension (LRH), where captopril had practically no effect. The different chronic BP response in relation to initial renin activity may indicate different mechanisms or modalities of action. Following the recommended doses and administration intervals of captopril and enalapril, the latter seems more effective, but there seems to be no difference in tolerability.