Progesterone-PLGA in situ formed implants: Structural parameters correlations with in vitro and in vivo mathematical models

Abstract

Drug controlled release systems are widely studied in the pharmaceutical and veterinary industry to improve therapies effectiveness. During the present investigation, in situ implants containing progesterone were prepared by using biodegradable poly (D,L-lactide-co-glycolic) polymer and phase inversion technique. N-methyl-2-pyrrolodone, glycerol formal and dimethyl sulfoxide were used as partially water-soluble solvents for the implant formulations. Encapsulation efficiencies, structural morphologies and mathematical modeling of in vitro release were studied. Concerning encapsulation efficiencies, all of them were higher than 60%. Implants structures and porosities depended on the solvent and drug to polymer ratio. The proposed in vitro swelling-diffusive model showed the best adjustment for all the implants. In addition, two formulations were selected for dairy cows performance experiments. Results showed that progesterone concentrations could not be maintained over the basal plasma levels during more than 24-48 h. The in vivo mathematical modeling performance was probably affected by the in vitro-in vivo implants morphologic differences.