Development of a directly compressible poly(ethylene oxide) matrix for the sustained-release of dihydrocodeine bitartrate.

The purpose of this study was to design and evaluate a directly compressible hydrophilic poly(ethylene oxide) (PEO) matrix for the oral sustained delivery of dihydrocodeine bitartrate (DHCT). A direct compression method was used to prepare PEO matrices, and the amount of PEO in the matrices was varied to optimize in vitro DHCT release profiles. In vitro release studies indicated that the matrices containing 20%-70% w/w of PEO with molecular weight of 5.0 x 10(6) showed a similar release profile, as estimated with DT50%, to that exhibited by a marketed product, DHC Continus. In vivo bioavailability study revealed that the difference in the pharmacokinetic parameters such as AUC0-30 and Tmax of the selected sustained-release formulation containing 60% w/w of PEO 5.0 x 10(6) and DHC Continus was statistically insignificant (p > 0.05). Thus, it could be concluded that the extent of bioavailability of the sustained-release formulation developed here was similar to that of DHC Continus although Cmax values of these two preparations were significantly different (p < 0.05). From the data obtained in this research, hydrophilic PEO matrices were found to be a novel sustained-release carrier for the oral delivery of DHCT.