Comparison of once and twice daily administration of captopril plus hydrochlorothiazide on 24 h blood pressure levels.

The anti-hypertensive effect of captopril 50 mg plus hydrochlorothiazide 25 mg, given once or twice daily, was investigated by 24 h monitoring in hypertensive patients in a controlled, randomized, double-blind, cross-over trial. Ten patients with blood pressure (BP) greater than 160 and/or 95 mm Hg after a 15 day placebo period, were randomly assigned to one of two treatments, in which they either received the combination once daily in the first month, twice daily in the second and once daily in the third (Treatment Group A) or twice daily in the first month, once daily in the second month and twice daily in the third month (Treatment Group B). The anti-hypertensive effect of the drug combination was assessed by 24 h monitoring using a Dinamap 845 to establish mean BP levels and circadian curves. After 1 month the twice daily administration was more effective than the once daily, but after 2 months, and throughout the third month, there was no difference in the anti-hypertensive efficacy of the combination given either once or twice daily.