INVIVO PEPTIDE RELEASE FROM POLY(DL-LACTIC ACID-CO-GLYCOLIC ACID) COPOLYMER 50/50 MICROSPHERES

Amorphous poly(DL-lactic acid-co-glycolic acid) copolymers 50/50 are used to prepare biodegradable carriers for drug delivery formulations. A luteinizing hormone-releasing hormone agonist, triptoreline, is incorporated in small microspheres and obtained by a phase separation technique in non-aqueous medium. The microspheres are injected by the intramuscular route in the thigh of male rats. The rate of peptide release depends on the overall polymer hydrophobicity defined by the amount of residual oligomers present and technology variables. The best release results are obtained from microspheres prepared at 2500 rpm (high preparative stirring speed) and with polymer P2 (intermediate hydrophobicity) which ensures complete castration in rats over one month.