Pharmacokinetic and pharmacodynamic studies with long-acting propranolol.

The whole blood concentrations of propranolol have been compared, over a 48 h period, in twelve healthy male volunteers dosed with a 160 mg long-acting capsule formulation (LA, United Kingdom patent application No. 23114/77) and three standard tablet regimens; 160 mg once a day (CP160), 80 mg twice a day (CP80) and 40 mg four times a day (CP40). The mean peak blood level for the long-acting formulation was significantly lower than that obtained with the 160 mg standard tablet. However, from 12 h on the mean levels for the long-acting formulation were higher. The mean peak blood level for the long-acting formulation was significantly lower than that obtained with the 80 mg twice a day regimen and this difference was maintained up to 24 h. Thereafter, however, the situation was reversed. The mean blood levels between 12 and 15 h were lower for the long-acting formulation when compared with the 40 mg four times a day regimen. At all other times, however, the observed levels were very similar. The profiles achieved with the long-acting formulation in two separate studies were almost identical over a 48 h period. The percentage reductions in exercise heart rate over the 3-24 h post dosing period were similar for the long-acting formulation and the two standard regimens studied (i.e. CP40 and CP80) when compared with placebo. In the 2 h post dosing period the 80 mg twice a day regimen produced a significant reduction in the post-exercise systolic blood pressure when compared with the long-acting formulation.