In vitro Release Kinetics of Progesterone from Biodegradable In situ Implant System

Abstract

In situ implants containing Progesterone (PRG) were prepared by using biodegradable Poly (DLlactide-
co-glycolide) polymer. Dimethyl sulfoxide (DMSO) was used as an aprotic solvent in this implant
formulation. This system was prepared by dissolving a water insoluble and biodegradable polymer (PLGA) in a
biocompatible organic solvent (DMSO) and then the drug progesterone was added to the polymer solution to produce
the drug solution. When the PLGA-PRG solution (0.5 ml) was injected subcutaneously into rat (weight 130g), the
solvent dissipated into the surrounding tissue leading phase separation and subsequent coagulation of the polymer &
drug to form an implant in situ. The implants were removed from the rat after one hour and stored in freezing
condition. The digital photographs of the in-situ formed implants obtained after 1hour shows the evidence of the
formation of the implants. Two formulations of implants were made. One contained 10% of progesterone and the
other 20%. In vitro dissolution studies of progesterone was performed at static condition in ethanol-water mixture
(30:70) at 37°C for 30 days. The implants of 20% progesterone loading showed about 65% release and the implants
of 10% loading showed 56% release within 30 days. The release mechanism from these implants resembles closely to
Higuchian pattern and first order. The release rate was found faster from the implants with higher drug loading of
20% progesterone, compared to implants of 10% drug loading.