A multiple dose comparative study of the pharmacodynamic and pharmacokinetic behaviour of polymer-matrix and Oros dosage forms of oxprenolol in healthy volunteers.

A new osmotic drug delivery system (Oros) has been evaluated in multiple-dose studies in young healthy volunteers as a sustained-release vehicle for once-daily administration of oxprenolol. Two Oros systems were examined in two separate studies, one containing 170 mg oxprenolol succinate with an initial zero-order release rate of 10 mg/h, and the other containing 260 mg oxprenolol succinate with an initial release rate of 16 mg/h. These were compared respectively with conventional oxprenolol hydrochloride (Trasicor) 80 mg twice daily and polymer-matrix oxprenolol hydrochloride (Slow Trasicor) 160 mg once daily. Variations in mean plasma levels and beta-adrenoceptor blockade (measured by inhibition of exercise tachycardia) were considerably reduced on the 10/170 Oros once-daily compared with the Trasicor 80 mg twice-daily regimen. With both formulations there was no significant change in mean plasma concentrations or areas under the curve after 8 days' treatment, and similar pre-dose plasma concentrations were obtained. There was significant inhibition of exercise tachycardia throughout 24 h after the 10/170 Oros on the eighth day. The 16/260 Oros system gave smoother pharmacokinetic and pharmacodynamic profiles, and on repeated dosing a higher mean pre-dose plasma oxprenolol concentration than Slow Trasicor. Drug availability was similar for the two dose forms, suggesting an acceptable level of absorption of oxprenolol from most of the gastrointestinal tract. On the eighth day exercise heart rate was significantly reduced throughout 24 h with 16/260 oxprenolol Oros, but only between 1 and 15 h with Slow Trasicor.