Formulation and evaluation of mefenamic acid sustained release matrix pellets.

The objective of the study was to prepare mefenamic acid (MA) sustained release matrix pellets and investigate the formulation parameters affecting pellet attributes and drug release in vitro. Amixer torque rheometer (MTR) was used to characterize the rheological properties of wet mass used in pellet formulation. Mefenamic acid pellets were prepared by extrusion/spheronization techniques using microcrystalline cellulose (MCC) in combination with lactose as pellet forming agents and water as the binding liquid. Also, the prepared pellets were characterized for their particle size and in vitro drug dissolution. The results revealed that the increase in lactose weight ratio to MCC resulted in a significant reduction of both maximum torque and binder ratios, while the addition of 2 % (m/m) polyvinyl pyrolidone (PVP) to MCC-lactose influenced only the mean torque rather than the wetting liquid (water). Particle size ranged from 945 to 1089 mm and had small span values (0.56-0.67). Furthermore, an inverse relation was observed between the rheological character of pellet wet masses (expressed by peak torque) and in vitro release rate. Increasing MAloading from 2.5 to 5 and 10 % was accompanied by a decrease in dissolution rates. In conclusion, properties of MA matrix pellets could be successfully monitored by controlling the wet mass characteristics by measuring torque.