Modification of release rates of cyclosporin A from polyl(L-lactic acid) microspheres by fatty acid esters and in-vivo evaluation of the microspheres.

Biodegradable microspheres containing cyclosporin A (CyA, cyclosporine) were prepared using poly(L-lactic acid) (PLA) and poly(lactide-co-glycolide)(PLGA) by a solvent evaporation method. CyA was efficiently entrapped in PLA, PLGA(50/50) and PLGA(75/25) microspheres in a range of 81-85%. CyA released constantly from PLA microspheres without any lag time, whereas the drug from PLGA(50/50) and PLGA(75/25) microspheres was released after lag time of about 1 and 3 weeks, respectively. Addition of fatty acid esters enhanced the release rates of CyA from PLA microspheres. In-vivo study was performed using rats with adjuvant-induced arthritis. PLA microspheres with ethyl myristate sustained high blood levels of CyA compared with the microspheres with no additives over 4 weeks. In addition, the PLA microspheres improved the symptoms such as the decrease in body weight and the increase in paw swelling occurred by adjuvant-induced arthritis in rats. Consequently, the release rate of CyA from PLA microspheres can be improved by adding fatty acid esters and PLA microspheres with fatty acid esters seem to be a useful dosage form for autoimmune disease therapy.