In this study, effect of solvent system on in vitro granisetron HCl release from injectable in situ forming implants were investigated also by means of gamma irradiation sterilization. Implant formulations contain 56% solvent, 38% polymer and 6% drug. For the preparation of the formulations, hydrophobic benzyl benzoate and moderately hydrophobic prophylene carbonate were used as solvents while medium molecular weight poly(DL-lactide-co-glycolide) (Resomer RG 503H) was used as polymer and the formulation containing the solvents in 1:1 combination showed low initial burst and acceptable regular release of drug for 21 days. It was determined that drug release from this formulation was increased by application of gamma irradiation and the sterilization effect were investigated on solidified implant system by the morphological analysis, which used as descriptive for in vitro release behavior of drug. In vivo performance of the mentioned sterile formulation was investigated on rabbits and it was determined that plasma drug concentrations reached to steady state on 10 to 21 days. As a conclusion encouraging results were obtained for the investigation of in situ implant systems.

Keywords: Injectable, In situ implant, Granisetron HCl, Poly(DL-lactide-co-glycolide), Rabbit.