Emergency contraception emergency contraceptive pills

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [2]

Overview

Emergency contraceptive pills (ECPs)—sometimes simply referred to as emergency contraceptives (ECs) or the "morning-after pill"—are drugs that act both to prevent ovulation or fertilization and possibly post-fertilization implantation of a blastocyst (embryo). ECPs are distinct from medical abortion methods that act after implantation.[1]

Emergency Contraceptive Pills

Template:Seealso Emergency contraceptive pills (sometimes referred to as emergency hormonal contraception (EHC) in the U.K.) may contain higher doses of the same hormones (estrogens, progestins, or both) found in regular combined oral contraceptive pills. Taken after unprotected sexual intercourse, such higher doses may prevent pregnancy from occurring. Mifepristone is another kind of ECP, but is considered an anti-hormonal drug, and does not contain estrogen or progestins.

The phrase "morning-after pill" is figurative; ECPs are licensed for use up to 72 hours after sexual intercourse.

Types of ECPs

The progestin-only method uses the progestin levonorgestrel in a dose of 1.5 mg, either as two 750 μg doses 12 hours apart, or more recently as a single dose. Progestin-only EC is available as a dedicated emergency contraceptive product under many names worldwide, including: in the U.S., Canada and Honduras as Plan B; in the U.K., Ireland, Australia, New Zealand, Portugal and Italy as Levonelle; in 44 nations including France, most of Western Europe, India, and several countries in Africa, Asia and Latin America as NorLevo; and in 44 nations including most of Eastern Europe, Mexico and many other Latin American countries, Portugal, Australia and New Zealand, Israel, China, Hong Kong, Taiwan and Singapore as Postinor-2.[2]

The combined or Yuzpe regimen uses large doses of both estrogen and progestin, taken as two doses at a 12-hour interval. This method is now believed to be less effective and less well-tolerated than the progestin-only method.[3] It is possible to obtain the same dosage of hormones, and therefore the same effect, by taking several regular combined oral contraceptive pills. For example, 4 Ovral pills are the same as 4 Preven pills.[4][5] The FDA approved this off-label use of certain brands of regular combined oral contraceptive pills in 1997.[4][6][7]

The drug mifepristone may be used either as an ECP or as an abortifacient, depending on whether it is used before or after implantation. In the USA, it is most commonly used in 200- or 600-mg doses as an abortifacient,[8] but in China it is commonly used as emergency contraception. As EC, a low dose of mifepristone is slightly less effective than higher doses, but has fewer side effects.[9] As of 2000, the smallest dose available in the USA was 200 mg.[10] Mifepristone, however, is not approved for emergency contraceptive use in the United States.[11] A review of studies in humans concluded that the contraceptive effects of the 10-mg dose are due to its effects on ovulation,[12] but understanding of its mechanism of action remains incomplete. Higher doses of mifepristone can disrupt implantation and, unlike levonorgestrel, mifepristone is effective in terminating established pregnancies.

Morning-after pills (ECPs) are not to be confused with the “abortion pill”, otherwise known as RU486, mifestone, or Mifeprex. According to the International Federation of Gynecology and Obstetrics, “EC is not an abortifacient because it has its effect prior to the earliest time of implantation.” Since they act before implantation, they are considered medically and legally to be forms of contraception.

Effectiveness of ECPs

Progestin-only (levonorgestrel) regimen:

The original (1999) FDA-approved U.S. product labeling for Plan B said:

Plan B reduces the risk of pregnancy following a single act of unprotected sex from about 8% down to 1%. This represents an 89% reduction in risk of pregnancy for this single act of unprotected sex.[13]

The current (2006) FDA-approved U.S. product labeling for Plan B says:

Plan B works best the sooner you use it. If it is taken within 72 hours (3 days) after sex, it will significantly decrease the chance that you will get pregnant. Seven out of every 8 women who would have gotten pregnant will not become pregnant. Plan B works even better than this if taken within the first 24 hours after sex.[14]

Combined (Yuzpe) regimen:

The original (1998) FDA-approved U.S. product labeling for Preven (the Yuzpe regimen), referring to Yuzpe regimen ECPs, said:

If one hundred women used ECPs correctly in one month, about two women would become pregnant after a single act of intercourse. If no contraception is used about eight women would become pregnant after a single act of intercourse. Therefore, the use of ECPs results in a 75% reduction in the number of pregnancies to be expected if no ECPs were used after unprotected intercourse. Notably some clinical trials have shown that efficacy was greatest when ECPs were taken within 24 hours of unprotected intercourse, decreasing somewhat during each subsequent 24-hour period.[15]

The effectiveness of emergency contraception is expressed as a percentage reduction in pregnancy rate for a single use of EC. A review article in American Family Physician explains the 75% effectiveness rate of the Yuzpe regimen thus:

... these numbers do not translate into a pregnancy rate of 25 percent. Rather, they mean that if 1,000 women have unprotected intercourse in the middle two weeks of their menstrual cycles, approximately 80 will become pregnant. Use of emergency contraceptive pills would reduce this number by 75 percent, to 20 women.[16]

Mifepristone regimen:

In three randomized trials providing individual data of mifepristone 10 mg taken up to 120 hours (5 days) after intercourse, the combined estimate of pregnancies prevented was 83%.[17] In high quality trials, mifepristone 10 mg had similar effectiveness to mifepristone 25-50 mg, which had similar effectiveness to levonorgestrel 1.5 mg.[18][19]

The effectiveness of emergency contraception is highest when taken within 12 hours of intercourse and declines over time.[20][21] The limit of 72 hours is based on a study by the World Health Organization (WHO).[3] A subsequent WHO study has suggested that reasonable effectiveness continues for up to 120 hours (5 days) after intercourse.[19] However, many doctors (particularly in the U.K.) advise use of an IUD rather than ECPs for emergency contraception between 72 and 120 hours.[citation needed]

Effectiveness estimate calculation

Early studies of emergency contraceptives did not attempt to calculate a failure rate, they simply reported the number of women who became pregnant after using an emergency contraceptive. Since 1980, clinical trials of emergency contraception have estimated effectiveness using: observed pregnancies divided by the estimated (by cycle day) number of women who would have become pregnant without treatment.[22]

In their April 2007 emergency review article, Trussell and Raymond note:

Calculation of effectiveness, and particularly the denominator of the fraction, involves many assumptions that are difficult to validate. Therefore, reported figures on the efficacy of emergency contraception may be underestimates or, more probably, overestimates. Yet, precise estimates of efficacy may not be highly relevant to many women who have had unprotected intercourse, since ECPs are often the only available treatment. A more important consideration for most ECP clients may be the fact that data from both clinical trials and mechanism of action studies clearly show that at least the levonorgestrel regimen of ECPs is more effective than nothing.[23]

  • Eight studies of the progestin-only (levonorgestrel) regimen, that included more than 9,500 women, reported effectiveness estimates between 59% and 94%.[23]
  • A meta-analysis of eight studies of the combined (Yuzpe) regimen, that included more than 3,800 women and reported effectiveness estimates between 56% and 89%, concluded that the best point estimate of effectiveness was 74%.[23][24]
  • A more recent analysis of two of the largest combined (Yuzpe) regimen studies, using possibly more accurate estimates of conception probabilities by cycle day, found effectiveness estimates of 47% and 53%.[3][23][25][26]
  • Combined data from two randomized trials that directly compared the two regimens, found the levonorgestrel regimen was twice as effective as the Yuzpe regimen.[3][18][23][27][28]

Placebo-controlled trials that could give a precise measure of effectiveness for EC would be unethical, so the effectiveness percentage is estimated. This is currently done using variants of the calendar method.[29] Women with irregular cycles for any reason (including recent hormone use such as oral contraceptives and breastfeeding) must be excluded from such calculations. Even for women included in the calculation, the limitations of calendar methods of fertility determination have long been recognized. Recently, hormonal assay has been suggested as a more accurate method of estimating fertility for EC studies.[30]

Safety

Existing pregnancy is not a contraindication in terms of safety, as there is no known harm to the woman, the course of her pregnancy, or the fetus if progestin-only or combined emergency contraception pills are accidentally used, but EC is not indicated for a woman with a known or suspected pregnancy because it is not effective in women who are already pregnant.[23][31][32][33][34][35][36][37]

The WHO Medical Eligibility Criteria for Contraceptive Use list no medical condition for which the risks of emergency contraceptive pills (using progestin-only or combined oral contraceptive pills) outweigh the benefits, specifically noting breastfeeding and history of ectopic pregnancy as conditions where there are no restrictions on use of ECPs, and history of severe cardiovascular disease (heart attack, stroke, blood clots), angina, migraine, and severe liver disease (including jaundice) as conditions where the advantages of using emergency contraceptive pills generally outweigh the theoretical or proven risks.[35] The American Academy of Pediatrics (AAP) and experts on emergency contraception say progestin-only ECPs may be preferable to combined ECPs containing estrogen in women with a history of blood clots, stroke, or migraine.[23][31][32]

The AAP, American College of Obstetricians and Gynecologists (ACOG), U.S. Food and Drug Administration, the WHO, the Royal College of Obstetricians and Gynaecologists's Faculty of Family Planning & Reproductive Health Care (FFPRHC) and other experts on emergency contraception state that there are no medical conditions in which progestin-only ECPs are contraindicated.[23][31][32][33][34][35][36] The FFPRHC UK Medical Eligibility Criteria for Contraceptive Use specifically note current venous thromboembolism, current or past history of breast cancer, inflammatory bowel disease, and acute intermittent porphyria as conditions where the advantages of using emergency contraceptive pills generally outweigh the theoretical or proven risks.[36]

The herbal preparation of St John's wort and some enzyme-inducing drugs (e.g. anticonvulsants or rifampicin) may reduce the effectiveness of ECP, and a larger dose may be required.[38][39]

The AAP, ACOG, FDA, WHO, FFPRHC and experts on emergency contraception say that ECPs, like all other contraceptives, reduce the absolute risk of ectopic pregnancy by preventing pregnancies, and that the best available evidence, obtained from over 7,800 women in randomized controlled trials, indicates there is no increase in the relative risk of ectopic pregnancy in women who become pregnant after using progestin-only ECPs.[23][31][32][33][34][35][36][37][38][40]

Side effects

The most common side effect of emergency contraceptive pills is nausea (50% of users of combined pills, 23% of progestin-only users), and a significant number of users vomit. Estrogen in combined ECPs is responsible for the increased incidence of nausea and vomiting. Antiemetics may be prescribed for both methods, to be taken 1 hour before each ECP dose. If vomiting occurs within an hour after taking ECP's, it may be necessary to repeat the dose.

Other common side effects are abdominal pain, fatigue, headache, dizziness, and breast tenderness. These side effects normally resolve within 24 hours.

Temporary disruption of the menstrual cycle is also commonly experienced. If taken before ovulation, the high doses of progestogen in levonorgestrel treatments may induce progestogen withdrawal bleeding a few days after the pills are taken. One study found that about half of women who used levonorgestrel ECPs experienced bleeding within 7 days of taking the pills.[41] If levonorgestrel is taken after ovulation, it may increase the length of the luteal phase, thus delaying menstruation by a few days.[42] Mifepristone, if taken before ovulation, may delay ovulation by 3-4 days.[43] (Delayed ovulation may result in a delayed menstruation.) These disruptions only occur in the cycle in which ECPs were taken; subsequent cycle length is not significantly affected.[41] If a woman's menstrual period is delayed by a week or more, it is advised that she take a pregnancy test.[44] (Earlier testing may not give accurate results.)

Postcoital high-dose progestin-only oral contraceptive pills as ongoing contraception

One brand of levonorgestrel pills, Postinor, is marketed as an ongoing method of postcoital contraception.[45] However, there are serious drawbacks to such use of postcoital high-dose progestin-only oral contraceptive pills, especially if they are not used according to their package directions, but are instead used according to the package directions of emergency contraceptive pills:

  • Due to the increasing severity of side effects with frequent use, Postinor is only recommended for women who have intercourse four or fewer times per month.[45][46]
  • If not used according to their package directions, but instead used according to the directions of levonorgestrel emergency contraceptive pills (up to 72 hours after intercourse), they would be estimated to have a "perfect-use" (when not used according to their package directions but used as directed on the package directions for levonorgestrel emergency contraception pills) pregnancy rate of 20% per year when used as the sole means of contraception (as compared to a 40% annual pregnancy rate for the Yuzpe regimen).[47] These failure rates would be higher than those of almost all other birth control methods, including the rhythm method and withdrawal.[48]
  • Like all hormonal methods, postcoital high-dose progestin-only oral contraceptive pills do not protect against sexually transmitted infections.[49]

ECPs are generally recommended for backup or "emergency" use, rather than as the primary means of contraception. They are intended for use when other means of contraception have failed—for example, if a woman has forgotten to take a birth control pill or when a condom is torn during sex.[47]

References

  1. ↑ A minority view in the medical community, along with many pro-life advocates, argue for a different definition of pregnancy; see Controversy section for more detail.
  2. ↑ Trussell, James; Wynn, Lisa (2007-06-28). "Emergency Contraceptive Pills Worldwide". Princeton University. Retrieved 2007-06-30.
  3. ↑ 3.0 3.1 3.2 3.3 WHO Task Force on Postovulatory Methods of Fertility Regulation (1998). "Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception". Lancet. 352 (9126): 428–33. PMID 9708750.
  4. ↑ 4.0 4.1 OPR & ARHP (2007-06-18). "Emergency contraception: Pill brands, doses, and instructions". Princeton University. Retrieved 2007-06-30.
  5. ↑ OPR & ARHP (2007-06-18). "Ovral". Princeton University. Retrieved 2007-06-30.
  6. ↑ FDA (1997-02-25). "Certain combined oral contraceptives for use as postcoital emergency contraception". Fed Regist. 62 (37): 8610–2.
  7. ↑ Weiss, Deborah; Friedman, Deborah (2006-12-13). "Emergency contraception". PPFA. Retrieved 2007-06-30.
  8. ↑ "Planned Parenthood - Mifepristone: Expanding Women's Options for Early Abortion". Unknown parameter |accessyear= ignored (|access-date= suggested) (help); Unknown parameter |accessmonthday= ignored (help)
  9. ↑ Piaggio G; et al. (2003). "Meta-analysis of randomized trials comparing different doses of mifepristone in emergency contraception". Contraception. 68 (6). PMID 14698075.
  10. ↑ Wertheimer, Randy E. (2000-11-15). "Emergency Postcoital Contraception" (HTML). American Family Physician. American Academy of Family Physicians. Retrieved 2006-07-23. Check date values in: |date= (help)
  11. ↑ Ho, Pak Chung, et. al (2002)."Mifepristone: Contraceptive and Non-Contraceptive Uses." Current Opinions in Obstetrics Gynecology, 14(3), 325-230.
  12. ↑ Gemzell-Danielsson, K. (2004-06-10). "Mechanisms of action of mifepristone and levonorgestrel when used for emergency contraception" (HTML). Human Reproduction Update. Oxford University Press. 10 (4): 341–348. Retrieved 2006-07-23. Unknown parameter |coauthors= ignored (help); Check date values in: |date= (help)
  13. ↑ FDA (1999). "Plan B label information" (PDF). Retrieved 2007-07-03. Unknown parameter |month= ignored (help)
  14. ↑ FDA (2006). "Plan B label information" (PDF). Retrieved 2007-07-03. Unknown parameter |month= ignored (help)
  15. ↑ FDA (1998). "Preven label information" (PDF). Retrieved 2007-07-03. Unknown parameter |month= ignored (help)
  16. ↑ Weismiller D (2004). "Emergency contraception". Am Fam Physician. 70 (4): 707–14. PMID 15338783.
  17. ↑ Piaggio G, Heng Z, von Hertzen H, Bilian X, Linan C (2003). "Combined estimates of effectiveness of mifepristone 10 mg in emergency contraception". Contraception. 68 (6): 439–46. PMID 14698074.
  18. ↑ 18.0 18.1 Cheng L, Gulmezoglu AM, Oel CJ, Piaggio G, Ezcurra E, Look PF (2004). "Interventions for emergency contraception". Cochrane Database Syst Rev (3): CD001324. PMID 15266446.
  19. ↑ 19.0 19.1 von Hertzen H, Piaggio G, Ding J, Chen J, Song S, Bartfai G, Ng E, Gemzell-Danielsson K, Oyunbileg A, Wu S, Cheng W, Ludicke F, Pretnar-Darovec A, Kirkman R, Mittal S, Khomassuridze A, Apter D, Peregoudov A; WHO Research Group on Post-ovulatory Methods of Fertility Regulation (2002). "Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: a WHO multicentre randomised trial". 360 (9348): 1803–10. PMID 12480356. Unknown parameter |journa= ignored (help)
  20. ↑ "Counsel women to take ECPs as soon as possible". Contracept Technol Update. 20 (7): 75–7. 1999. PMID 12295381.
  21. ↑ WHO/HRP (1999). "Levonorgestrel is more effective, has fewer side-effects, than Yuzpe regimen". Prog Hum Reprod Res (51): 3–5. PMID 12349416.
  22. ↑ Dixon GW, Schlesselman JJ, Ory HW, Blye RP (1980). "Ethinyl estradiol and conjugated estrogens as postcoital contraceptives". JAMA. 244 (12): 1336–9. PMID 6251288.
  23. ↑ 23.0 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 Trussell J, Raymond EG (2007). "Emergency contraception: a cost-effective approach to preventing unintended pregnancy" (PDF). Princeton University. Retrieved 2007-07-03. Unknown parameter |month= ignored (help)
  24. ↑ Trussell J, Rodriguez G, Ellertson C (1999). "Updated estimates of the effectiveness of the Yuzpe regimen of emergency contraception". Contraception. 59 (3): 147–51. PMID 10382076.
  25. ↑ Trussell J, Ellertson C, von Hertzen H, Bigrigg A, Webb A, Evans M, Ferden S, Leadbetter C (2003). "Estimating the effectiveness of emergency contraceptive pills". Contraception. 67 (4): 259–65. PMID 12684144.
  26. ↑ Ellertson C, Webb A, Blanchard K, Bigrigg A, Haskell S, Shochet T, Trussell J (2003). "Modifying the Yuzpe regimen of emergency contraception: a multicenter randomized controlled trial". Obstet Gynecol. 101 (6): 1160–7. PMID 12798518.
  27. ↑ Ho PC, Kwan MS (1993). "A prospective randomized comparison of levonorgestrel with the Yuzpe regimen in post-coital contraception". Hum Reprod. 8 (3): 389–92. PMID 8473453.
  28. ↑ Raymond E, Taylor D, Trussell J, Steiner MJ (2004). "Minimum effectiveness of the levonorgestrel regimen of emergency contraception". Contraception. 69 (1): 79–81. PMID 14720626.
  29. ↑ Trussell J, Ellertson C, Stewart F (1996). "The effectiveness of the Yuzpe regimen of emergency contraception". Fam Plann Perspect. 28 (2): 58–64, 87. PMID 8777940.
  30. ↑ Espinos JJ, Rodriguez-Espinosa J, Senosiain R, Aura M, Vanrell C, Gispert M, Vega C, Calaf J (1999). "The role of matching menstrual data with hormonal measurements in evaluating effectiveness of postcoital contraception". Contraception. 60 (4): 243–7. PMID 10640171.
  31. ↑ 31.0 31.1 31.2 31.3 AAP Committee on Adolescence (2005). "Emergency contraception" (PDF). Pediatrics. 116 (4): 1026–35. PMID 16147972.
  32. ↑ 32.0 32.1 32.2 32.3 Grimes DA, Raymond EG (2002). "Emergency contraception" (PDF). Ann Intern Med. 137 (3): 180–9. PMID 12160366.
  33. ↑ 33.0 33.1 33.2 ACOG (2005). "ACOG Practice Bulletin, Number 69: Emergency contraception". Obstet Gynecol. 106 (6): 1443–52. PMID 16319278.
  34. ↑ 34.0 34.1 34.2 FDA (2006). "Plan B Rx to OTC switch Medical Reviews" (PDF). pp. pp. 32-7, 133–77. Retrieved 2006-12-13. Unknown parameter |month= ignored (help)
  35. ↑ 35.0 35.1 35.2 35.3 WHO (2004). "Emergency contraceptive pills". Medical eligibility criteria for contraceptive use (PDF) (3rd ed. ed.). Geneva: Reproductive Health and Research, WHO. ISBN 92-4-156266-8. Retrieved 2006-12-13.
  36. ↑ 36.0 36.1 36.2 36.3 FFRPHC (2006). "The UK Medical Eligibility Criteria for Contraceptive Use (2005/2006)" (PDF). Retrieved 2006-12-13. Unknown parameter |month= ignored (help)
  37. ↑ 37.0 37.1 Davidoff F, Trussell J (2006). "Plan B and the politics of doubt". JAMA. 296 (14): 1775–8. PMID 17032991.
  38. ↑ 38.0 38.1 FFRPHC (2006). "FFPRHC Guidance (April 2006). Emergency contraception" (PDF). J Fam Plann Reprod Health Care. 32 (2): 121–8. PMID 16824309.
  39. ↑ Joint Formulary Committee (2006). British National Formulary (52 ed.). London: British Medical Association; Pharmaceutical Society of Great Britain. ISBN 0-85369-669-1. Unknown parameter |month= ignored (help)
    FFRPHC (2006). "FFPRHC Guidance (April 2005). Drug interactions with hormonal contraception" (PDF). J Fam Plann Reprod Health Care. 31 (2): 139–51. PMID 15921558.
    FFRPHC (2006). "FFPRHC Guidance (July 2005). The use of contraception outside the terms of the product licence" (PDF). J Fam Plann Reprod Health Care. 31 (3): 225–41. PMID 16105289.
  40. ↑ Trussell J, Hedley A, Raymond E (2003). "Ectopic pregnancy following use of progestin-only ECPs". J Fam Plann Reprod Health Care. 29 (4): 249. PMID 14662065.
  41. ↑ 41.0 41.1 Raymond E, Goldberg A, Trussell J, Hays M, Roach E, Taylor D (2006). "Bleeding patterns after use of levonorgestrel emergency contraceptive pills". Contraception. 73 (4): 376–81. PMID 16531171.
  42. ↑ Gainer E, Kenfack B, Mboudou E, Doh A, Bouyer J (2006). "Menstrual bleeding patterns following levonorgestrel emergency contraception". Contraception. 74 (2): 118–24. PMID 16860049.
  43. ↑ Gemzell-Danielsson K, Marions L (2004). "Mechanisms of action of mifepristone and levonorgestrel when used for emergency contraception". Hum Reprod Update. 10 (4): 341–8. PMID 15192056.
  44. ↑ "ACOG Practice Bulletin. Clinical Management Guidelines for Obstetrician-Gynecologists, Number 69, December 2005. Emergency contraception". Obstet Gynecol. 106 (6): 1443–52. 2005. PMID 16319278.
  45. ↑ 45.0 45.1 Ellertson, Charlotte (March/April 1996). "History and Efficacy of Emergency Contraception: Beyond Coca-Cola". Family Planning Perspectives. Guttmacher Institute. 28 (2). Retrieved 2006-11-22. Check date values in: |date= (help)
  46. ↑ Chernev T, Ivanov S, Dikov I, Stamenkova R (1995). "Prospective study of contraception with levonorgestrel". Plan Parent Eur. 24 (2): 25. PMID 12290800.
  47. ↑ 47.0 47.1 "Effectiveness of Emergency Contraceptives". The Emergency Contraception Website. Office of Population Research at Princeton University and the Association of Reproductive Health Professionals. November 2006. Retrieved 2006-12-2. Check date values in: |accessdate= (help)
  48. ↑ Bakhtiar, Saadia (May 2000). "Contraception". Pakistan Journal of Family Medicine. 11: 19–24. Retrieved 2006-12-2. Unknown parameter |coauthors= ignored (help); Check date values in: |accessdate= (help)
  49. ↑ "What is Emergency Contraception?". The Emergency Contraception Website. Office of Population Research at Princeton University and the Association of Reproductive Health Professionals. November 2006. Retrieved 2006-12-2. Check date values in: |accessdate= (help)

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