Certain problems regarding the drugs like high first pass metabolism, also the bioavailability of the certain drugs varies due to instability in acidic environment of stomach. Hence, to resolve such problems the drug should be incorporated in the microspheres for sustained release using a suitable polymer. Natural polymer like chitosan gained great interest in pharmaceutical sector because of its advantages like biodegradability, biocompatibility, non-toxicity, non-immunogenicity and low cost.

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... n the present study, formulation and evaluation of polymeric microspheres of Atorvastatin Calcium was carried out and the release profile of such drug using the alginate and chitosan was studied. Microspheres were prepared for sustained release of drug using chitosan and alginate polymers by ionotropic gelation method. Microspheres were spherical in shape, having good flow properties and further its encapsulation efficiency, swelling index, micromeritic study, in- vitro drug release study and stability studies were performed in order to characterize microspheres. Three different concentrations of sodium alginate (1%, 2% and 3%) were used. The higher encapsulation efficiency was observed as the concentration of alginate increased. This is due to the greater availability of active calcium binding sites in the polymeric chains and consequently the greater degree of cross linking. The highest encapsulation efficiency (88.36) was achieved with 2% w/v sodium alginate in combination with 3% chitosan (F6). Among the prepared formulations with respect to the entrapment efficiency, swelling studies and in vitro drug release, the alginate-chitosan microspheres prepared by ionotropic gelation using calcium chloride found to be better than ionically cross linked alginate spheres alone. Therefore, dual cross-linked, microspheres are promising carrier for sustained release of drug.