Captopril withdrawal after chronic therapy

Sudden symptomatic increases in blood pressure may result from withdrawal of antihypertensive drug therapy. Captopril, an orally active angiotensin converting enzyme inhibitor, was abruptly withdrawn from the antihypertensive regimen of 6 patients (5 males; aged 31 to 58) with moderate to severe hypertension. The patients had received captopril (50-450 mg/day), diuretics, and in 2 cases, propranolol for 3-13 months; all drugs other than captopril were continued during the study. Blood pressure increased gradually in all patients from a mean (+/- SEM) of 135/92 +/- 5/2 mm Hg to 164/111 +/- 8/3 mm Hg in the 14 to 156 hours following captopril withdrawal, without the occurrence of symptoms. No "rebound" increase in blood pressure was noted. Plasma renin activity decreased, plasma aldosterone and serum angiotensin II concentrations increased and plasma catecholamine concentrations did not change during this time. These changes are consistent with the cessation of angiotensin converting enzyme inhibition. Reinstitution of captopril reduced blood pressure to the previous nadir suggesting a lack of tolerance to its effects after chronic therapy.