The morning after pill is a form of contraception. Also called "emergency contraception pills" or ECP and sometimes known by one of its brand names, "Plan B," the morning after pill is generally used as backup birth control when the primary contraception choice has failed. It is also routinely administered to women who have been sexually assaulted. ECP availability varies by state, with some states allowing it to be sold over-the-counter by pharmacists and some requiring a prescription before it can be purchased.
Different Types of ECP
Levonorgestrel-based ECPs are the type most commonly found in the U.S. as of 2011. The brand names available include Plan B One-Step and Next Choice. Levonorgestrel ECPs can be used for up to 72 hours after unprotected sex and are generally available over the counter for women age 17 and over. Levonorgestrel has been on the market for quite a few years, although it has only become more widely available in the 2000s.
The other type of ECP contains ulipristal acetate and goes by the brand name Ella. It has not been on the market for as long as levonorgestrel and does require a physician's prescription. Ulipristal acetate is effective for up to five days after unprotected sex.
In some cases, physicians may also use an intrauterine device, or IUD, to prevent pregnancy from occurring. This is a physical device placed in your uterus and is not a pill.
Availability of ECPs
Despite the length of time it has been on the market--oral contraceptives have been used off-label as ECPs since the 1960s--there continues to be some controversy surrounding the availability of the morning after pill. Because of the involved controversy, it can be difficult for many women to obtain ECPs.
Since some states still require a physician's prescription to obtain the morning-after pill, some health care providers suggest having a supply of ECPs on hand, just in case a contraceptive failure occurs at night, over the weekend or while you are traveling. Talk with your health care provider about this possibility.
How ECPs Work
Physician David Weismiller from the Brody School of Medicine published a thorough overview of emergency contraception in the August 2004 issue of "American Family Physician." In this article, Weismiller discusses how ECPs work to prevent pregnancy. In short, studies have reported vastly different findings on exactly why and how the morning-after pill prevents pregnancy. Some studies have reported changes in the endometrium, or uterine lining, that make pregnancy far less likely. Others have suggested that ECPs work by causing changes in the fallopian tubes that make it difficult for embryos to implant, thus preventing pregnancy. Still other studies found that ECPs actually prevent or delay ovulation in some women. Given the evidence available, Weismiller speculates that the most likely predominant way the morning-after pill functions is by causing endometrial changes or changes in the cervical mucus that make pregnancy less likely.
It is important to note that ECPs cannot terminate or end an existing pregnancy, they can only prevent pregnancy from occurring.
Effectiveness of ECPs
The effectiveness of ECPs varies depending on how soon after sexual intercourse you take them. If you are able to obtain and take the morning-after pill within 72 hours of unprotected sex, the general consensus is that your chance of becoming pregnant will be reduced by between 75 to 89 percent. A study published in the April 2003 issue of the medical journal "Contraception" reported findings that a woman who followed the prescribed regimen for taking ECPs has only a 5.3 percent chance of becoming pregnant.
According to Drugs.com, there is no known interaction between ECPs and multivitamins, and multivitamins are very unlikely to affect the effectiveness of the morning-after pill. There are some medications and herbals that can interact with levonorgestrel, however, including St. John's wort, nevirapine and rifampin. If you are taking any of those medications, tell your health care provider before ECPs are prescribed. Discuss any medication or supplements you take regularly, whether prescription or over the counter, with your physician before you receive a prescription for the morning-after pill.
References
- MayoClinic.com: Morning-after pill
- "American Family Physician"; Emergency Contraception; David Weismiller, MD, SC.M; August 2004
- "Contraception"; Effectiveness of the Yuzpe Regimen of Emergency Contraception by Cycle Day of Intercourse: Implications for Mechanism of Action; J. Trussell et al.; September 2003
- "Contraception"; Estimating the Effectiveness of Emergency Contraception; J. Trussell et al; April 2003
- Drugs.com: Levonorgestrel
- Drugs.com: Ella
