The influence of propranolol on the cardiovascular effects and plasma clearance of epinephrine.

The purpose of the present study was to determine how propranolol modifies the circulatory effects of epinephrine infused to produce plasma concentrations achieved during dental local anesthesia and to evaluate the effects of propranolol on the plasma clearance of epinephrine. The study was performed on six healthy male volunteers ranging in age from 25 to 34 yr. Five measurement series were performed on each of these subjects at the following times: pretreatment control, 15 min after the beginning of the first epinephrine infusion (10 ng/kg/min), 15 min after the cessation of the first epinephrine infusion, 3 min after the intravenous injection of propranolol 40 micrograms/kg, and 15 min after the beginning of the second epinephrine infusion. Plasma epinephrine clearance decreased to 54.7 +/- 9.3% of the control value after propranolol was given. Epinephrine showed initially a predominantly beta-adrenergic action, but this action was inhibited by propranolol. A relative alpha-dominant state may then occur, even when a routine volume of dental local anesthetic is administered to a chronic user of a nonselective beta blocker, and it is postulated that myocardial ischemia may develop in such patients.