Evaluation of the effect-duration of once-daily enalapril compared with once-daily captopril

The extent and duration of the antihypertensive effect of enalapril and captopril, both given once daily, were evaluated in 12 mild-to-moderate essential hypertensives by 24-hour noninvasive blood pressure (BP) monitoring (Pressurometer IV-mod 1990-1991, Del Mar Avionics). Patients were randomized to a cross-over regimen either with enalapril, 10-20 mg, followed by captopril, 50-100 mg (first group), or with captopril followed by enalapril (second group). The dose was doubled if, at week 3 of each treatment, the diastolic BP remained at 90 mm Hg. Doubling of the 2 drugs was not required in 4 patients; in 7 patients the dose of both drugs was doubled; and in 1 patient the dose of only captopril was doubled. Two of the 7 patients who required doubling of both drugs were considered nonresponders to enalapril and captopril. The circadian rhythm was not altered by the treatments, and the drugs reduced BP mainly during the waking hours. However, the second peak of systolic BP in the late afternoon did not graphically appear to be modified by captopril administration. A periodic asymmetric model with 3 harmonics analysis carried out on 24-hour BP data justifies only the use of enalapril for once-daily administration.