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.
levonorgestrel emergency contraception mechanism, Plan B mechanism of action, post-fertilization contraceptive effects, emergency contraception ovulation inhibition, levonorgestrel endometrial receptivity, abortifacient vs contraceptive debate, emergency contraception ethical considerations, LNG-EC pharmacology, hormonal emergency contraception luteal phase, Catholic health care emergency contraception
PMID 25698840 25698840 DOI 10.1179/2050854914Y.0000000026 10.1179/2050854914Y.0000000026
Cite this article
Kahlenborn, C., Peck, R., & Severs, W. B. (2015). Mechanism of action of levonorgestrel emergency contraception. The Linacre Quarterly, 82(1), 18-33. https://doi.org/10.1179/2050854914Y.0000000026
Kahlenborn C, Peck R, Severs WB. Mechanism of action of levonorgestrel emergency contraception. Linacre Q. 2015;82(1):18-33. doi:10.1179/2050854914Y.0000000026
Kahlenborn, C., et al. "Mechanism of action of levonorgestrel emergency contraception." The Linacre Quarterly, vol. 82, no. 1, 2015, pp. 18-33.
Keywords
Abortion, Early Pregnancy Factor, Levonorgestrel Emergency Contraception, Moral Certitude
Recent studies have identified that levonorgestrel administered orally in emergency contraception (LNG-EC) is only efficacious when taken before ovulation. However, the drug does not consistently prevent follicular rupture or impair sperm function. The present systematic review is performed to analyze and more precisely define the extent to which pre-fertilization mechanisms of action may explain the drug's efficacy in pregnancy avoidance. We also examine the available evidence to determine if pre-ovulatory drug administration may be associated with post-fertilization effects. The mechanism of action of LNG-EC is reviewed. The drug has no ability to alter sperm function at doses used in vivo and has limited ability to suppress ovulation. Our analysis estimates that the drug's ovulatory inhibition potential could prevent less than 15 percent of potential conceptions, thus making a pre-fertilization mechanism of action significantly less likely than previously thought. Luteal effects (such as decreased progesterone, altered glycodelin levels, and shortened luteal phase) present in the literature may suggest a pre-ovulatory induced post-fertilization drug effect. Plan B is the most widely used emergency contraceptive available. It is important for patients and physicians to clearly understand the drug's mechanism of action (MOA). The drug was originally thought to work by preventing fertilization. Recent research has cast doubt on this. Our review of the research suggests that it could act in a pre-fertilization capacity, and we estimate that it could prevent ovulation in only 15 percent or less of cases. The drug has no ability to alter sperm function and limited ability to suppress ovulation. Further, data suggest that when administered pre-ovulation, it may have a post-fertilization MOA.
The Ethical and Religious Directives for Catholic Health Care Services allows the use of an emergency contraceptive for a woman who has been raped, as a defense against her attacker's sperm, provided the drug prevents fertilization and does not act against a conceived human life. Catholic emergency rooms around the country have been pressured to provide Plan B (LNG-EC) to patients seeking help after a sexual assault. Catholic bioethicists have supported the use of this drug based on their interpretation of the scientific literature regarding its mechanism of action. This paper presents a review of the mechanisms of action of LNG-EC when given during the fertile window, showing a high probability that it acts against human life rather than preventing fertilization, and proposes another class of drugs as a possible alternative.
To investigate the sociological, environmental, and economic impact of hormonally active contraceptives, a series of comprehensive literature surveys were employed. Sociological effects are discussed including abortion, exploitation of women, a weakening of marriage, and an increase in divorce with deleterious effects on children such as child poverty, poorer health, lower educational achievement, suicide risks, drug and alcohol abuse, criminality, and incarceration, among others. The environmental impact is discussed briefly and includes the feminization and trans-gendering of male fish downstream from the effluent of city wastewater treatment plants with declining fish populations. The potential economic impact of most of these side effects is estimated based on epidemiologic data and published estimates of costs of caring for the diseases which are linked to the use of hormonally active contraceptives. Hormonally active contraceptives appear to have a deleterious impact on multiple aspects of women's health as well as negative economic and environmental impacts. These risks can be avoided through the use of nonhormonal methods and need to be more clearly conveyed to the public.
Hormonal contraceptives have wide-ranging effects. The potential economic impact of the medical side effects is estimated. Sociological effects are discussed including abortion, exploitation of women, a weakening of marriage and an increase in divorce with negative effects on children such as child poverty, poorer health, lower educational achievement, suicide risks, drug and alcohol abuse, criminality and incarceration among others. The environmental impact includes hormonal effects on fish with declining fish populations. Women seeking birth control have a right to know about how to avoid these risks by using effective hormone-free methods like Fertility Awareness Methods.
Hormonal contraceptives have been on the market for over fifty years and, while their formulations have changed, the basic mechanism of action has remained the same. During this time, numerous studies have been performed documenting side effects, some of which appear over time, some within weeks or months, but all can have a serious impact on health and quality of life. An effort was made to perform a series of comprehensive literature surveys to better understand immediate and long-term side effects of these agents. The results of this literature review uncovered a number of potential side effects, some of which are acknowledged and many of which are not noted in the prescribing information for these agents. Among the unacknowledged an increased risk of HIV transmission for depot medroxyprogesterone acetate (DMPA), and for combination contraceptives breast cancer, cervical cancer, Crohn's disease, ulcerative colitis, systemic lupus erythematosus, depression, mood disorders and suicides (especially among women twenty-five years of age and younger, in the first six months of use), multiple sclerosis, interstitial cystitis, female sexual dysfunction, osteoporotic bone fractures (especially for progesterone-only contraceptives), and fatty weight gain. Misleading prescribing information regarding cardiovascular and thrombotic risks are also noted. Women seeking birth control have a right to be informed and educated about risk avoidance through the use of effective nonhormonal methods like fertility awareness methods. In one case-that of DMPA-the increased risk of HIV acquisition has been conclusively demonstrated to be both real and unique to this drug. Considering the availability of numerous alternatives, there is no justification for the continued marketing of DMPA to the public.
We reviewed the effect of hormonal contraceptives on women's health. A number of potential side effects were noted including increased risks of breast cancer, cervical cancer, inflammatory bowel disease, lupus, multiple sclerosis, cystitis, bone fractures, depression, mood disorders and suicides, fatty weight gain, and female sexual dysfunction. With the long-acting injectable contraceptives there is an increased risk of getting HIV. Misleading prescribing information regarding the risks of heart attacks, strokes and blood clotting problems were also noted. Women seeking birth control have a right to know about how to avoid these risks by using effective hormone-free Fertility Awareness Methods.