STUDY OF RELEASE KINETICS OF DEXAMETHASONE FROM BIODEGRADABLE PLGA IN-SITU IMPLANTS

The primary objective of this study is to evaluate the effect of drug loading and the effect of excipients on the release pattern of Dexamethasone Sodium Phosphate from in situ PLGA implants formed in vitro in gelatin gel. This system is prepared by dissolving a biodegradable polymer (DL-PLGA 70K) in dimethyl sulfoxide (DMSO). Then the drug with excipients or without excipients was added to it. When the drug solution poured into the hallow of gelatin gel, the solvent dissipates into the surrounding gelatin base through diffusion leading phase separation & subsequent coagulation of the polymer and the drug to form a rod like implant in situ. Two types of implants were prepared such as implants containing Dexamethasone Sodium Phosphate and implants containing Dexamethasone Sodium Phosphate with biocompatible excipients such as Tween 20, Tween 60, Span 20, Span 80, Chremophore EL, Chremophore RH40, Stearyl alcohol, Cetyl alcohol, PEG 6000, Stearic acid, GMS, Benzyl Benzoate, Magnesium stearate, Dextrose, Lactose and Arachis oil were used. In vitro dissolution studies were performed in static condition using phosphate buffer (pH 7.4) to observe the release of drugs from these implants. Formulation containing only Dexamethasone Sodium Phosphate showed that drug loading was 86.82%, 90.60%, 87.47%, 91.79% and 92.78% against the actual drug content of 9.09%, 13.04%, 16.67%, 20% and 23.08% respectively. The release rate was 64.51%, 70.64%, 74.08%, 76.12% and 80.05 % respectively. It can be said that telease rate of drug increase with the increase in concentration of drug and Dexamethasone releases faster due to its hydrophilicity. On the other hand formulation containing Dexamethasone with excipients the release rate was 62.21%, 73.06%, 77.42%, 79.95% and 81.52%. For implants containing Dexamethasone with excipients the release rate were different due to their characteristics. It can be concluded from the experiment that although excipient lowers the release rate of drug, these can prolong the activity and the overall release kinetics is increased than that can be obtained from implants without excipients.