The effect of dosage release formulations on the pharmacokinetics of propranolol stereoisomers in humans.

Recent studies in dogs have suggested that the disposition of S- and R-propranolol may depend on the input rate of drug delivered to the liver. Therefore, this study was designed to determine whether differences in the disposition of S- and R-propranolol occur in humans when altering the input rate of propranolol by giving different dosage forms of the drug. Twelve healthy subjects were enrolled in a single-dose, 4-way crossover pharmacokinetic study in which racemic propranolol was given according to 1 of 4 treatments: one 80-mg immediate-release (IR) tablet, phase A; two 80-mg IR tablets, phase B; a 160-mg controlled-release capsule, phase C; or a 10-mg IV bolus, phase D. The results showed no significant differences in the ratios of S/R-propranolol for AUC, clearance, or overall mean concentration among the oral dosage groups. Significant differences in these parameters including Cmax S/R ratio were seen between the oral phases and the IV phase. These differences appear to be related more to the route of administration than to the low input rate. However, at high concentrations there may be input-rate alteration in S/R ratios. Specifically, for phase B, which had the highest Cmax concentrations, the Cmax S/R ratio was significantly lower than the other oral dosage groups A and C (Cmax S/R ratios: 1.44 versus 1.54 and 1.54, respectively; P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)