PROPOSED STRATEGIES FOR IMPROVING THE STABILITY OF POLYMERIC HPMC MATRIX TABLETS: PROPER SELECTION OF EXCIPIENTS AND SEAL COATING

Pharmaceutical materials are adversely affected when exposed to moisture during manufacturing or storage due to moisture uptake. In this research work, a strategy was proposed to improve stability of previously prepared extended release HPMC matrix tablets of diclofenac sodium (DS) that showed functional instability during storage. The hypothesis was to decrease water sorption with either of two approaches. The first one comprised the choice of lactose anhydrous as a diluent with a lower initial moisture content instead of lactose monohydrate. The second approach comprised sealing of tablets via creating a continuous protective film of Kollicoat (R) Smartseal in order to achieve protection against moisture uptake. All the prepared formulations showed initial similar drug release profile to each other and to the marketed product with comparable release efficiency and mean dissolution time values. The DS release from F2 (mannitol as a diluent) was significantly increased in long term conditions (RE 88%, MDT 2.7h and f(2) value 42.05 as compared to the initial condition). F3 (anhydrous lactose as a diluent) showed stable drug release on storage (f(2) values were in the range 69.99-83.16). The sealed formulations at coat levels 2, 4 and 9% w/w showed stable drug release on storage with acceptable f(2) values (61.11-79.87) whereas significant retardation in drug release was demonstrated with only coat level 15% w/w at long term conditions. No change in drug content was observed in any formulation. Both strategies improved the stability of the tablets during storage, however optimizing the coat level is essential otherwise it can adversely affect the drug release rate.