Enalapril Versus Triple-drug Therapy in the Treatment of Renovascular Hypertension

18 renovascular hypertensive patients were entered into a randomised, double-blind protocol to assess the safety and efficacy of enalapril (5 to 20 mg twice-daily) and hydrochlorothiazide (50 to 100 mg/day), versus triple-drug therapy employing hydrochlorothiazide (50 to 100 mg/day), timolol (10 to 30 mg twice-daily) and hydralazine (50 to 150 mg twice-daily). Specifically monitored were the effects of each drug regimen on blood pressure, plasma renin activity and angiotensin II, glomerular filtration rate by insulin clearance, and effective renal plasma flow by para-aminohippurate clearance. Results indicate that enalapril/hydrochlorothiazide was more effective than triple-drug therapy in lowering blood pressure. All patients on enalapril/hydrochlorothiazide had excellent control of blood pressure, and there were no adverse effects. In contrast, 50% of the patients on triple-drug therapy had either uncontrolled blood pressure or significant drug-related side effects. Patients who were uncontrolled or intolerant of triple-drug therapy were well controlled on enalapril/hydrochlorothiazide. Patients on enalapril/hydrochlorothiazide demonstrated stimulation of plasma renin activity with inhibition of plasma angiotensin II, indicating adherence with therapy. Therapy for both unilateral and bilateral renovascular hypertension with enalapril/hydrochlorothiazide did not result in reductions in either glomerular filtration rate or effective renal plasma flow, except in 1 patient with a functional solitary stenotic kidney. In contrast, triple-drug therapy was generally associated with modest reductions in glomerular filtration rate and effective renal plasma flow, with a severe reduction in glomerular filtration rate and effective renal plasma flow occurring in 1 patient with bilateral symmetrical renovascular disease. We conclude that the combination of enalapril and hydrochlorothiazide is a safer and more effective regimen, compared with triple-drug therapy, for the treatment of renovascular hypertension.