A comparison of slow release with conventional oxprenolol: plasma concentrations and clinical effects.

1 Plasma concentrations of oxprenolol have been compared in six healthy volunteers after 80 and 160 mg doses of a new slow release (SR) oxprenolol preparation, after an 80 ng dose of conventional oxprenolol (CO), and after the second of two 80 mg doses of conventional oxprenolol given 12 h apart. Basal pulse rates and blood pressures, and pulse rates before and after a standard exercise test have been compared after the four active treatments and after a placebo. 2 Peak plasma concentrations of oxprenolol attained after 160 mg of the slow release preparation were similar to the peak concentrations after the single 80 mg dose of conventional oxprenolol. Higher concentrations, however, persisted for much longer after the slow release preparations than after the conventional preparations. 3 Neither oxprenolol formulation had any effect on resting pulse rate or blood pressure in normotensive volunteers. 4 Comparison with placebo showed that the single dose of the conventional oxprenolol produced a significant reduction in exercise induced tachycardia for 8 h whereas the high dose of the slow release preparation produced a similar reduction which lasted for at least 14 hours.