The objective of the current investigation is to formulate ethyl cellulose based sustained release microspheres, containing metformin hydrochloride and glipizide as model drugs. Metformin and glipizide both are type II antidiabetic agents when administered together shows synergetic effect in their action. Microspheres were prepared by W/O/O double emulsion solvent diffusion method with different stabilizer concentration and at different speeds of emulsification while maintaining constant amounts of metformin and glipizide. Drug excipient compatibility study was performed prior to formulation development and only compatible excipients were used in the fabrication of microspheres. Prepared microsphere formulations were characterized by percentage yield, particle size analysis, entrapment efficiency, invitro release behavior, differential scanning colorimetry (DSC) and scanning electron microscopy (SEM). SEM studies showed that the microspheres were spherical with rough surface morphology. The drug loaded microspheres showed 29-90% entrapment capacity for metformin and 6-21% entrapment capacity for glipizide. The invitro release profile showed a slow and steady release pattern for both metformin and glipizide. A 100% metformin was releases within a period of 12 hrs while only 46% glipizide was released during this time. The drug release was found to be diffusion controlled mechanism. The n value of Korsmeyer Peppas equation indicated non Fickian type of diffusion. DSC results indicated that the physical state of the drug was changed upon fabrication. As a result of these experiments, it was conclude that, novel sustained release oral microspheres comprising a combination of metformin and glipizide were successfully prepared using ethyl cellulose as the polymer and using double emulsion solvent diffusion technique.
