Serum mifepristone level and effect of mifepristone-releasing implants on the endometriosis in rats

Objective To observe the serum mifepristone levels and the inhibitory effect of mifepristone-releasing implants on the endometriosis in rats. Methods The normal rats and the rats with endometriosis were subdermally implanted a piece of the 0.75,1.5,3.0 cm,2 or 3 pieces of 3.0 cm lenth of mifepristone-releasing implants resepectively. The serum levels of mifepristone in normal rats were determined by HPLC. The changes of volumes of explants in rat with endometriosis were measured by MRI at 1,2,3 months after administration. Results The peak concentrations of mifepristone found in all normal rats at the 7th days and increased in proportion to dose. After 7 days,the serum levels of mifepristone decreased gradually. After administration 14 days,the concentrations of serum mifepristone in all normal rats(about 0.10 ～ 0.13 μg/ml) showed no significant differences with rats implanted 3 pieces of 3.0 cm lenth of mifepristone-releasing implants(about 0.18 ～ 0.20 μg/ml).Administration of 1/2,1,2 pieces of 3.0 cm lenth of mifepristone-releasing implants resulted in inhibitory rates of 18.6 % ± 17.3 %,31.5 % ± 12.7 % and 72.2 % ± 12.3 % respectively at 1 month. But administration of 3 pieces 3.0 cm lenth of implants,better inhibitory effects were not observed. Conclusion It is demonstrated that subcutaneous administrating mifepristone-releasing implant shows obvious therapautical effect on endometriosis.