左旋18—甲基炔诺酮经阴道给药的药代动力学和药效...

Pharmacokinetic and pharmacodynamic studies on vaginally administered levonorgestrel]

This paper discusses the pharmacokinetics of the vaginal application of levonorgestrel (LNG); its effect on the foundation of the ovary, and a pharmacokinetic comparison of oral administration and vaginal application of LNG, in order to develop a steroid contraceptive for external use and to identify the appropriate dosage. Six health women of child-bering age who had regular menstrual period and had child-bearing experiences in the past five years were recruited in the study. The subjects were given one cycle of LNG Positnor externally, and one cycle orally. A blood sample was taken before and after the administration in order to test the LNG concentration. Observation of serum estrogen and progesterone concentration after both oral and external administration indicated obvious suppression of ovarian function. Daily fluctuations and individual variations of LNG serum concentration during the cycle of external administration were large. A comparison of the pharmacodynamics of administering Postinor through two different media shows that oral administration led to faster effects, but the dosage may need to be reduced to preserve the contraceptive effect while reducing the impact of the drug on the body. Vaginal administration of Postinor led to slower absorption; and the peak value serum LNG concentration was only 1/3 of the oral administration, which indicates that the formulation needs to be modified to increase the usefulness. As the suppression of ovarian function and a fluctuation in LNG serum concentration was clearly manifested with an administration of every two days, a change in regimen to a daily administration of a reduced dosage may be considered.