Captopril, an orally active converting enzyme inhibitor, in the treatment of primary hypertension. A controlled long-term study with reference to initial plasma renin activity.

Captopril (SQ 14 225), an orally active inhibitor of angiotensin converting enzyme, was evaluated in the treatment of primary (essential) hypertension in a placebo-controlled long-term study. In 24 patients allocated to captopril treatment, mean supine BP fell from 174 +/- 18/110 +/- 7 to 151 +/- 22/96 +/- 12 mmHg. Ten patients achieved a supine diastolic BP of less than or equally 90 mmHg with a mean BP fall of 28/22 mmHg after 4 weeks' captopril dose titration (75-450 mg daily). In 14 patients, BP fell 19/9 mmHg. When hydrochlorothiazide (50-100 mg daily) was subsequently added, a total supine BP reduction of 51/20 mmHg was noted. In the placebo control group (n = 16), BP changed +1/-2 mmHg from 171/110 mmHg while addition of hydrochlorothiazide caused a mean supine BP fall of 19/10 mmHg. During long-term follow-up (mean 11.8 months), no resistance to therapy developed. A weak correlation, (p less than 0.05) was seen between pretreatment plasma renin activity and initial captopril-induced BP reduction. However, in patients with clearly defined low renin hypertension, the hypotensive effect of captopril was much less than in patients with higher renin values. Captopril induced a significant decrease in urinary aldosterone excretion, which was partially reversed by addition of hydrochlorothiazide. Observed side-effects were proteinuria (1 case), rash (2 cases) and taste disturbances (3 cases). During long-term follow-up, seven patients have dropped out, four due to side-effects and three because of non-compliance.