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

There is no general agreement on the relation between the hypotensive effect of captopril and the pretreatment plasma renin levels of hypertensive patients. To determine whether the hypotensive effect of captopril was directly related to plasma renin, the angiotensin-converting enzyme inhibitor was administered acutely to 10 essential hypertensive patients with normal or suppressed plasma renin activity before and after inhibition of renin secretion with propranolol. Captopril was equally effective in reducing blood pressure both when administered alone (25 mg: -29/-17; 50 mg: -37/-23 mm Hg) and after chronic treatment with propranolol (25 mg: -33/-20; 50 mg: -30/-20 mm Hg). The increase in renin induced by captopril was not decreased by propranolol therapy. The persistence of the hypotensive effect of captopril after renin suppression by propranolol suggests that this drug has some blood pressure decreasing properties independent of plasma renin.