Mechanism of Action of Levonorgestrel Emergency Contraception

Abstract

There has been much debate regarding levonorgestrel emergency contraception's (LNG-EC's) method of action since 1999 when the Food and Drug Administration first approved its use. Proponents of LNG-EC have argued that they have moral certitude that LNG-EC works via a non-abortifacient mechanism of action, and claim that all the major scientific and medical data consistently support this hypothesis. However, newer medical data serve to undermine the consistency of the non-abortifacient hypothesis and instead support the hypothesis that preovulatory administration of LNG-EC has significant potential to work via abortion. The implications of the newer data have important ramifications for medical personnel, patients, and both Catholic and non-Catholic emergency room protocols. In the future, technology such as the use of early pregnancy factor may have the potential to quantify how frequently preovulatory LNG-EC works via abortion. Lay Summary: How Plan B (levonorgestrel emergency contraception) works has been vigorously debated ever since the Food and Drug Administration approved it in 1999. Many doctors and researchers claim that it has either no-or at most-an extremely small chance of working via abortion. However, the latest scientific and medical evidence now demonstrates that levonorgestrel emergency contraception theoretically works via abortion quite often. The implications of the newer data have important ramifications for medical personnel, patients, and both Catholic and non-Catholic emergency room rape protocols.

Clinical Pharmacology of Hormonal Emergency Contraceptive Pills

“…Some authors have supported the view that emergency contraception is a form of abortion arguing that preovulatory administration of levonorgestrel as an emergency contraceptive has significant potential to work via abortion [ 14 , 33 ]. Conventionally, any drug or device that acts after implantation is termed an abortifacient rather than a contraceptive [ 34 ].…”

β-Lactoglobulin and Glycodelin: Two Sides of the Same Coin?

“…UPA on the other hand, has a decreasing effect as ovulation approaches but, since it blocks progesterone receptors, prevents implantation ( Mozzanega et al, 2014 ). Mozzanega and Nardelli (2019) consider the mechanisms of LNG and UPA from the viewpoint of informed consent since there is significant ethical concern if the action is directed toward the conceptus ( Kahlenborn et al, 2015 ; Peck et al, 2016 ).…”

Emergency Contraception Types and Mechanism of Actions

“…Nevertheless, the Yuzpe regimen may still have a role in restricted resource settings in which the more beneficial EC methods cannot be easily gained, or for women with prepared access to combined oral contraceptives. Women who have had coitus near the time of ovulation are at greater risk of pregnancy and should be particularly encouraged to use additional effective EC methods [4] .…”