Shukla A J, Price J C
School of Pharmacy, Duquesne University, Pittsburgh, Pennsylvania 15282.
Pharm Res. 1989 May;6(5):418-21. doi: 10.1023/a:1015939600866.
Three particle sizes (450, 120, and 5 microns) of theophylline were encapsulated in low molecular weight cellulose acetate propionate (intrinsic viscosity, 1.08 dl/g) by the solvent evaporation method. The theoretical drug content for all the batches of microspheres was 50% (w/w). Particle size analysis revealed that about 50% of the microspheres containing the large theophylline crystals (average length of 450 microns) were greater than 500 microns in diameter, whereas only about 35% of the microspheres containing the medium drug crystals (average length of 120 microns) were greater than 500 microns in diameter. The drug content of the larger microspheres prepared from the large drug crystals and the medium drug crystals was much greater than the theoretical drug content (50%, w/w); however, the drug content of all the batches of microspheres containing micronized drug was close to 50% (w/w). Release of the drug in simulated intestinal fluid was very rapid from microspheres containing large and medium drug crystals, while release was slower and more predictable from microspheres made from micronized drug.
采用溶剂蒸发法将三种粒径（450、120和5微米）的茶碱包封于低分子量醋酸丙酸纤维素（特性粘度为1.08 dl/g）中。所有批次微球的理论药物含量均为50%（w/w）。粒径分析显示，约50%含有大尺寸茶碱晶体（平均长度为450微米）的微球直径大于500微米，而仅约35%含有中等尺寸药物晶体（平均长度为120微米）的微球直径大于500微米。由大尺寸药物晶体和中等尺寸药物晶体制备的较大微球的药物含量远高于理论药物含量（50%，w/w）；然而，所有批次含有微粉化药物的微球的药物含量均接近50%（w/w）。在模拟肠液中，含有大尺寸和中等尺寸药物晶体的微球药物释放非常迅速，而由微粉化药物制成的微球释放较慢且更具可预测性。
