Maintenance of the antihypertensive efficacy of captopril despite consistent reduction in daily dosage.

1 After a period of 7 +/- 1.4 months of good control of hypertension by thrice daily administration of captopril (85 +/- 9 mg three times a day), captopril was given twice daily and the total dose was progressively reduced to sometimes very low levels in 12 patients. Twice daily administration of captopril 85 +/- 9 mg did not modify blood pressure control. 2 During reduction of captopril dosage to a minimum of 36 +/- 4 mg twice a day, the acute effect of the morning dose of captopril (last dose taken at least 12 hours before study) was assessed. Administration of the morning dose induced a decrease in mean arterial pressure from 112 +/- 4 mm Hg (104 +/- 3 mm Hg during administration of 85 +/- 9 mg) three times a day to 106 +/- 4 mm Hg, an increase in plasma renin activity, and a decrease in plasma aldosterone concentration. 3 These acute effects of captopril suggest that blood pressure was well controlled in the presence of a non-blocked circulating angiotensin-converting-enzyme activity, thus raising the possibility of alternate mechanisms by which captopril reduces arterial pressure. 4 The daily dosage of captopril needed to control hypertension may be reassessed after a certain period of good blood pressure control with 50 to 100 mg captopril three times a day.