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| Prescription research and release mechanism of mifeipristone EVA intravaginal ring |
| 1. National Research Institute for Family Planning, Beijing 100081；2.Graduate School of Peking Union Medical College |
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Abstract To prepare a mifepristone EVA intravaginal ring used for preoperative pretreatment or long-term management of women with uterine fibroids, to optimize the prescription of the intravaginal ring, to investigate the in vitro release rate of mifepristone of the intravaginal ring, and to preliminarily explore the mifepristone release mechanism of the intravaginal ring. Methods: Mifepristone EVA matrix-type and reservoir-type intravaginal rings were prepared by hot melt extrusion and coextrusion methods, respectively. The saturation solubility of mifepristone in different dissolution media was measured to select the appropriate dissolution medium. The paddle method was used to determine the in vitro release of mifepristone from the intravaginal ring. The single factor examination method was used to investigate the influence of the different parameters of the intravaginal ring on the in vitro release of mifepristone. The regularity of the in vitro release of mifepristone from intravaginal rings was summarized, and the formula of the in vitro release of mifepristone was fitted. Results: EVA28+EVA18 and EVA33+EVA28 were selected to prepare mifepristone reservoir-type intravaginal ring. The membrane thickness and the diameter of drug cores of the two intravaginal rings were 0.03 mm and 6.3 mm. The average daily drug release (MDR) of mifepristone of the EVA28+EVA18 and EVA33+EVA28 mifepristone reservoir-type intravaginal rings were 4.16 mg/d and 4.54 mg/d. The formula of the in vitro release of mifepristone intravaginal rings matches well with the experimental results. Conclusion: The in vitro release of mifepristone from the prepared intravaginal ring can meet the demand of low-dose administration of mifepristone for long-term management of uterine fibroids. The fitted formula of the mifepristone in vitro release from the intravaginal rings can guide the optimization of the intravaginal ring prescription to a certain extent.
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