Effect of Propranolol on the Renin Response to Frusemide in Man

The response of plasma renin activity (PRA) to frusemide, 40 mg given intravenously, was examined before and after oral propranolol 160 mg daily for seven days in normal and hypertensive subjects. Although basal PRA was reduced in many cases, the increase following frusemide was essentially unaltered by propranolol therapy. Evidence is presented that adequate beta adrenoceptor blockade was attained in these studies. Increasing the dose of propranolol to 240 mg daily for seven days in two subjects did not alter renin responsiveness to frusemide. Stimulation of renin release by oral frusemide, examined in one subject, was also unaltered by propranolol therapy. These findings indicate that enhancement of renin activity associated with diuretic use may not be prevented by concurrent propranolol administration. Limitation of the hypotensive action of combined beta blocker-diuretic therapy can therefore be expected. The fact that the renin stimulating effect of frusemide is preserved during beta blockade indicates that this procedure can be used in the investigation of hypertension even in those patients in whom discontinuation of beta blocking treatment may be undesirable.