Acute hypotensive and renin-stimulating actions of captopril before and during treatment with a beta-blocking drug

Single administration of captopril and combined use with beta-blocker and/or thiazide diuretic in the treatment of essential hypertension

Thirty-four patients with essential hypertension at WHO stage I or II were divided into three groups. Group I consisted of 22 cases who displayed normal renin activity (NR) or low renin activity (LR) and who received a single administration of captopril. Group II consisted of 6 cases given beta-blockers after administration of captopril. Group III consisted of 6 cases in whom beta-blocker was replaced with thiazide diuretics after administration of captopril alone. Blood pressure decreased significantly by captopril treatment alone in group I of the NR and LR subgroups (except for the diastolic blood pressure [DBP] of the NR subgroup) and fell below the target blood pressure (SBP of 165 mmHg and DBP of 95 mmHg) in 86% of the NR subgroup and 73% of the LR subgroup. Combined treatment with captopril and beta-blocker in Group II did not decrease blood pressure any lower than with captopril alone treatment and achieved the target blood pressure in only 50% of the patients. In group III, combined treatment with captopril and thiazide achieved the target blood pressure in 100% of the patients. Plasma renin activity (PRA) was increased by captopril but reduced by captopril in combination with beta-blocker. However, when beta-blocker was replaced with thiazide, PRA increased. The serum sodium concentration was significantly reduced in the LR subgroup after a single administration of captopril, but there was no other variation.