Development of lipid micromatrices based sustained release tablets of glipizide: suitability of stearic acid as release retardant

The objective of research was to explore the suitability of lipids like compritol 888 ATO and stearic acid as release retardant to develop sustained release (SR) tablets. The SR micromatrices of lipid (s) and glipizide were prepared (LM1- LM6) as intermediate product by fusion method and assessed for various pharmacotechnical properties. Micromatrices were formulated as SR tablets (F1-F6) by direct compression method and subjected to Pharmacopoeial and Non Pharmacopoeial tests.  In vitro drug release behavior of SR tablets demonstrated incomplete release of drug from compitrol based formulations whereas stearic acid based formulations (F4-F6) released more than 90% drug in 12 h with F5 displaying  maximum %CDR of  95.70 ± 0.78%. A t50% of 3 h exhibited by F5 was significantly lower (2.7 h) than of marketed formulation (Glytop SR® (t50% = 5.7 h)). Similarity and dissimilarity factor for F5, with reference to Glytop SR® was 21.65% and 26.34% respectively, suggesting F5 has potential to exercise better control on drug release. Scanning Electron Microscopy (SEM) revealed drug particles embedded in stearic acid micromatrices that were confirmed by The X-ray powder diffraction (XRPD) and simultaneously Diffuse Reflectance Infrared Fourier Transform (DRIFT) confirmed the stability of F5. Conclusively, stearic acid explored as a suitable lipidic release retardant for development of SR tablet of glipizide that were stable for the test period of 6 months.