Comparison of the pharmacokinetics of intravenous dl-propranolol in borderline and permanent hypertension.

In borderline and permanent hypertensives after rapid i.v. injection of dl-propranolol 0.2 mg/kg plasma levels were measured and were fitted to a two-compartment open-model. In borderline patients, characterized by a high basal cardiac output (CO), plasma levels were always lower than in permanent hypertensives. The biological half-life was reduced and the central volume of distribution, volume of distribution at pseudo-equilibrium and total clearance (TC) were markedly increased. In the overall population, there was a significant positive correlation between CO and TC. Rapid achievement of a predetermined plateau in each group constituted experimental proof of the validity of the two-compartment open-model for kinetic analysis of propranolol i.v. If kinetic parameters from permanent hypertensive were applied to borderline hypertensives a lower plateau was obtained. Thus, in so far as beta-blockade is related to plasma level of propranolol, an increased intravenous dose may be required in patients with high CO.