Comparison of once-daily captopril or enalapril in mild essential hypertension

The purpose of this study was to assess the effect of a daily low dose of the angiotensin-converting enzyme (ACE) inhibitors, captopril or enalapril, in mild essential hypertension. Nine men with seated diastolic blood pressure between 95 and 104 mm Hg on placebo participated in the study. After one month of placebo, captopril 25 mg was administered; blood pressure, heart rate, ACE activity and plasma renin activity were measured hourly for 4 hours. Each patient then received captopril 50 mg once daily for 8 weeks and similar measurements were made 24 hours post-dose every 2 weeks. After another month of placebo, the identical protocol was repeated after enalapril 5 mg. Although blood pressure and ACE activity decreased significantly (P less than 0.05) within 2-4 hours of the acute doses of each inhibitor, neither captopril or enalapril produced significant reductions 24 hours after the small daily dose. Thus, neither ACE inhibitor alone was adequate to control blood pressure in mild hypertension when given once daily during 8 weeks of treatment.