Clinical experience with converting-enzyme inhibitors in hypertension

Because the renin-angiotensin system frequently participates in sustaining severe forms of hypertension, early studies with the angiotensin-converting enzyme inhibitor captopril were concentrated in patients whose hypertension was refractory to previously available treatment. The effectiveness of captopril, both acutely and during long-term treatment, led to its widespread use for treatment-resistant hypertension. More recently, captopril's efficacy when used as monotherapy and its relative avoidance of symptomatic adverse effects have expanded its role to hypertension of all degrees of severity. A second converting-enzyme inhibitor, enalapril, has been approved for the treatment of hypertension. Its efficacy and clinical characteristics appear similar to those of captopril. In double-blind clinical trials, comparisons with beta-blocker or diuretic therapy have shown captopril to be equal in efficacy but to produce fewer side effects or metabolic changes. In mild-to-moderate essential hypertension it is effective when administered in twice-daily doses of 25 or 50 mg; higher doses do not usually increase its BP-lowering effects. The combination of captopril with a diuretic in low doses has been shown to be especially effective. In additional studies, once-daily doses have controlled BP in a majority of hypertensive patients, but this method of administering captopril has not yet been formally approved. In lower doses, captopril may be less effective in black patients than in white patients, but black patients appear to respond well if the doses are increased. Antihypertensive effects in elderly patients during captopril treatment are equal to those in the young. Converting-enzyme inhibitor therapy appears to have broad utility and a favorable side effect profile in the treatment of essential hypertension.