Design and evaluation of oseltamivir phosphate dual-phase extended-release tablets for the treatment of influenza

In this study, once-daily extended-release tablets with dual-phase release of oseltamivir phosphate were developed for the treatment of influenza. The goal was to improve patient adherence and offer more therapeutic choices. The tablets were manufactured using wet granulation, bilayer tablet compression, and enteric membrane-controlled coating processes. Various polymers, such as hydroxypropyl methylcellulose (HPMC K100MCR, K15MCR, K4MCR, K100LV), enteric polymers (HPMC AS-LF, Eudragit L100-55) and membrane-controlled polymers (OPADRY® CA), were used either individually or in combination with other common excipients. The formulations include enteric-coated extended-release tablet (F1), hydrophilic matrix extended-release tablet (F2), semipermeable membrane-controlled release tablet (F3) and a combination extended-release tablet containing both enteric and hydrophilic matrix (F4). The in vitro drug release profile of each formulation was fitted to the first-order model, and the Ritger-Peppas model suggested that Fickian diffusion was the primary mechanism for drug release. Comparative bioequivalence studies with Tamiflu® (oseltamivir phosphate) capsules revealed that formulations F1, F2, and F3 did not achieve bioequivalence. However, under fed conditions, formulation F4 achieved bioequivalence with a relative bioavailability of 95.30% (90% CI, 88.83%-102.15%). This suggests that the formulation F4 tablet could potentially be a new treatment option for patients with influenza.