The effect of polymer blends on release profiles of diclofenac sodium from matrices

The purpose of this study was to evaluate the effect of polymer blends on the in vitro release profile of diclofenac sodium. Several controlled release matrices of diclofenac sodium with different proportions of hydroxypropyl methylcellulose (HPMC; viscosity grade 60 and 500 mPa.s), carbopol 940 and lactose as a water soluble filler were prepared. The results showed that when HPMC (viscosity grade 60 mPa.s) alone was used as matrix former, diclofenac sodium was released fast but the release rate became slower with HPMC (viscosity grade 500 mPa.s) at higher polymer/drug ratios (more than 0.8:1). However in lower polymer/drug ratios (lower than 0.7:1) the release rate still was fast. The results showed that carbopol can extend the release time appreciably but the release profiles had considerable fluctuations, and drug release in first hours was slow but increased appreciably with time at the end of profiles. When an appropriate blend of HPMC (viscosity grade 60 or 500 mPa.s) and carbopol 940 was used, the drug release became more uniform and its kinetic approached to zero order and release fluctuations were diminished. The results with these polymer blends showed that it is possible to reduce the total amounts of polymer in each formulation. According to kinetic analysis data, drug release from these matrix tablets did not follow Fick's law of diffusion and the results were in agreement with the earlier reports.