Relative bioavailability of different oral sustained release oxprenolol tablets

The bioequivalence of oral dosage forms of oxprenolol was assessed in a triple crossover study on two groups of 12 volunteers each. Single 160 mg doses of oxprenolol hydrochloride were given after an overnight fast of either oxprenolol sustained-release tablets in a megaloporous system, a hydrophil matrix and Slow-Trasicor (Ciba-Geigy) in the first group, or floating slow-release tablets administered with food or in absence of food, and rapid release Oxprenolol (Terapia, Cluj-Napoca) tablets, in the second group. Serum oxprenolol concentrations were measured by a gas chromatographic method. Pharmacokinetic parameters which describe bioavailability and general kinetic behavior of the drug were calculated from individual serum profiles. They were subjected to statistical analysis (paired Student's t test, p < 0.05). The customary bioequivalence criterion was used: 0.8 < parameter ratio(tested/standard) < 1.2. Megaloporous tablets showed bioequivalence with the reference sustained release product Slow-Trasicor. Hydrophil tablets showed moderate sustained-release characteristics. Floating tablets showed significantly greater oxprenolol absorption when taken with food and were non-bioequivalent with floating tablets without food, as well as with the reference rapid release tablets, of oxprenolol. However, fasting tablets were bioequivalent to the Slow-Trasicor product, when taken with food.