PREPARATION AND CHARACTERIZATION OF COPOLY(DL-LACTIC GLYCOLIC ACID) MICROPARTICLES FOR SUSTAINED-RELEASE OF THYROTROPIN-RELEASING-HORMONE BY DOUBLE NOZZLE SPRAY-DRYING METHOD

Copoly(dl-lactic/glycolic acid) microparticles for sustained release o f a water soluble drug (Thyrotropin releasing hormone: TRH) were prepa red by a spray drying method. In the case of double nozzle spray dryin g (DNSD) using acetonitrile, the effect of TRH loading amount on the i nitial burst was smaller than that with in-water drying. The micropart icles prepared by DNSD and loaded with up to 10% TRH exhibited a small initial burst followed by a constant release rate over 4 weeks. The d rug release from the polymer was much faster than the polymer weight l oss. The mean particle size of the spray dried microparticles was smal ler than that with in-water drying. Acetonitrile used in DNSD is a les s toxic organic solvent than dichloromethane, and the residual amount in the microparticles was similar to that in the in-water drying metho d. In conclusion, the production of biodegradable microparticles by th e double nozzle spray drying method should be an attractive alternativ e to conventional microencapsulation methods.