Takada Shigeyuki

Preparation and characterization of copoly(dl-lactic/glycolic acid) microparticles for sustained release of thyrotropin releasing hormone by double nozzle spray drying method

Abstract Copoly(dl-lactic/glycolic acid) microparticles for sustained release of a water soluble drug (Thyrotropin releasing hormone: TRH) were prepared by a spray drying method. In the case of double nozzle spray drying (DNSD) using acetonitrile, the effect of TRH loading amount on the initial burst was smaller than that with in-water drying. The microparticles 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 drug release from the polymer was much faster than the polymer weight loss. The mean particle size of the spray dried microparticles was smaller than that with in-water drying. Acetonitrile used in DNSD is a less toxic organic solvent than dichloromethane, and the residual amount in the microparticles was similar to that in the in-water drying method. In conclusion, the production of biodegradable microparticles by the double nozzle spray drying method should be an attractive alternative to conventional microencapsulation methods.