Long-term effects of enalapril monotherapy and enalapril/hydrochlorothiazide combination therapy on blood pressure, renal function, and body fluid composition.

Enalapril, a potent long-acting angiotensin-converting enzyme inhibitor, was prescribed either alone (n = 9) or in combination (n = 20) with hydrochlorothiazide for 96 weeks in essential hypertensive subjects. Blood pressure was well controlled following both monotherapy or combination therapy. Plasma renin activity was stimulated in all subjects; plasma aldosterone concentration was stimulated only in subjects receiving combination therapy. Glomerular filtration rate (assessed by inulin clearance) was unchanged in subjects with initial clearances greater than 80 ml/min/1.73 m2 but was significantly improved (55%) following either form of therapy in subjects with initial clearances less than or equal to 80 ml/min/1.73 m2. Neither monotherapy nor combination therapy adversely affected 24-hour urinary protein excretion, sodium excretion, or body fluid composition. These results suggest that enalapril, either alone or in combination with hydrochlorothiazide, is effective therapy for mild to moderate hypertension. There are no adverse effect on renal function; indeed, enalapril has the capability of improving renal function in those subjects whose renal function was initially impaired from long-standing hypertension.