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Levonorgestrel as a postcoital contraceptive
B Shirley1, J C Bundren, S McKinney
1Department of Biological Sciences, University of Tulsa, OK 74104, USA.
Contraception
|November 1, 1995
Summary
Subdermal levonorgestrel implants can prevent pregnancy in mice by blocking embryo implantation. Effective contraception requires timely postcoital administration before day 3 to prevent uterine implantation.
Area of Science:
- Reproductive biology
- Pharmacology
Background:
- Norplant, a contraceptive system, utilizes levonorgestrel (LNG) for progestogenic effects.
- Understanding the postcoital timing for LNG efficacy is crucial for contraceptive development.
Purpose of the Study:
- To investigate the contraceptive potential of time-release levonorgestrel (LNG) implants.
- To determine the critical window for postcoital LNG administration to prevent embryo implantation in mice.
Main Methods:
- Subdermal implantation of LNG time-release pellets in mice post-mating.
- Varying implantation timing (day 0, 2, or 3 postcoital).
- Assessing pregnancy outcomes via embryo implantation counts, resorption rates, and term delivery.
Main Results:
- High-dose (5 mg/90 days) LNG pellets administered on day 0 completely prevented uterine implantation.
- On day 2, LNG pellets reduced implantation and caused resorption, preventing term pregnancies.
- Administration on day 3 failed to prevent implantation or term delivery.
Conclusions:
- Postcoital subdermal LNG implants can prevent pregnancy in mice by inhibiting uterine implantation.
- Effective contraception is achieved when LNG implants are administered before day 3 of the postcoital period.