Enalapril (MK421) in the treatment of hypertension with renal artery stenosis.

The converting enzyme inhibitor, enalapril, was given to 20 hypertensive patients with renal artery stenosis in a single daily dose of 10-40 mg. Enalapril effectively controlled hypertension long-term, and only two of the 20 patients required concomitant diuretic treatment. The blood pressure reduction 6 h after the first dose of enalapril was significantly related to pre-treatment plasma concentrations of active renin and angiotensin II (AII), and to the concurrent fall in AII. Blood pressure fell further with continued treatment; the long-term reduction was not significantly related to pretreatment plasma renin or angiotensin II. At three months, 24 h after the last dose of enalapril, blood pressure, plasma AII and converting enzyme activity remained low, and active renin and angiotensin I (AI) high; 6 h after dosing, AII had, however, fallen further. During prolonged therapy, the increase of active renin was proportionately greater than that of angiotensin I. Enalapril alone caused a long-term reduction in exchangeable sodium, with slight increases in serum potassium, creatinine and urea. Enalapril alone did not impair overall renal function in five patients with bilateral renal lesions despite effective blood pressure reduction. Enalapril was well tolerated with no serious side-effects. Enalapril given once daily is effective in controlling hypertension associated with renal artery stenosis.