JHPIEGO TrainerNews™ |
Contraceptive Technology Update:
Emergency Contraception
(May 2002)
Last month, JHPIEGO TrainerNews began featuring summaries of contraceptive technology updates that were presented in Washington, DC, in March 2002. Over the next several months, JHPIEGO staff members who attended these updates will share summaries of the sessions in which they participated. Although time and space constraints will limit the amount of detail, these summaries will focus on what is new and relevant internationally.
Dr. James Trussell (PhD, Princeton University), a leading authority in contraceptive technology, presented several sessions on emergency contraception (EC). Combined oral contraceptive pills (COCs), levonorgestrel-only pills (progestin-only pills or POPs), and the copper-bearing intrauterine device (IUD) are currently recommended methods for EC. This update focuses on combined and progestin-only emergency contraceptive pills (ECPs). In a later issue we will cover IUDs and discuss barriers to more widespread use of EC.
The following information is intended for trained and licensed medical practitioners. Any suggestions of possible treatment alternatives or administration of drugs or other therapy are stated for consideration of the treating professional only, after appropriate examination of or discussion with the patient, and in consideration of the patient's medical history and condition, and are not recommendations. All final treatment and medicating decisions must be made by the treating professional. There are several oral regimens for use in EC: a regimen of combined ECPs--ordinary COCs containing the hormones estrogen (ethinyl estradiol [EE]) and progestin (levonorgestrel or norgestrel)--sometimes called the Yuzpe regimen, progestin-only emergency contraceptives, and COCs that combine EE and norethindrone.
Dose
When using a dedicated combined EC product (i.e., one that is packaged specifically for use as an emergency contraceptive) the dose is 2 tablets within 72 hours of unprotected intercourse, followed 12 hours later by another 2 tablets. Dedicated combined EC products include Preven(r), which is available in the United States, and PC4(r), which is available in the UK, South Africa and Zambia. When a dedicated product is unavailable, standard monophasic COCs can be used. The number of pills to be taken will depend upon the formulation. For example, when using LoFemenal(r) or Lo/Ovral(r), 4 white pills would be used for each dose. A total of 100 to 120 micrograms EE and 0.5 to 0.75 mg of levonorgestrel per dose is needed.
For progestin-only ECPs the dose is 0.75 mg within 72 hours of unprotected intercourse, and a second dose of 0.75 mg 12 hours after the first dose. Currently, several progestin-only dedicated products are available for EC. Plan-B(r) is available in the United States and Postinor(r) is available in parts of Africa, Asia and Mexico. When a dedicated product is not available, 20 tablets of Ovrette(r), a commonly available progestin-only contraceptive can be used for each dose of EC.
Mechanism of Action
COCs act mainly by inhibiting ovulation. Although there are other possible mechanisms (e.g., trapping sperm in thickened cervical mucus; inhibiting tubal transport of the egg or sperm; interfering with fertilization, early cell division and transportation of the embryo; or impairing endometrial receptivity to implantation of a fertilized egg) there is little clinical data about these other mechanisms.
For progestin-only ECPs, inhibiting ovulation is the primary mechanism of action. But progestin-only ECPs may also act by altering uterine pH, which immobilizes the sperm, and by shortening the luteal phase of the menstrual cycle.
Effectiveness
When taken as described, combined ECPs reduce the risk of pregnancy by about 75 percent. This statement does not mean that 25 percent of women using ECPs will become pregnant. Rather, if 100 women had unprotected intercourse once during the second or third week of their cycle, about 8 women would become pregnant; following treatment with combined ECPs, only 2 women would become pregnant--a 75 percent reduction.
Of the progestin-only emergency contraceptives (i.e., those that contain no estrogen), only the progestin levonorgestrel has been studied for use in EC. Studies are currently being done on COCs that combine EE and norethindrone. Although preliminary results of these studies indicate some efficacy with this type of COC for EC, efficacy is probably less for this type of COC regimen than that of the Yuzpe or levonorgestrel-only regimens. The levonorgestrel regimen appears to be as effective as or more effective than the Yuzpe regimen. Progestin-only ECPs reduce the risk of pregnancy by 88 percent (i.e., with progestin-only ECPs,only 1 pregnancy will occur out of an expected 8 pregnancies without EC).
As the time between intercourse and the first dose of ECPs increases, the risk of pregnancy also increases. ECPs are most effective within the first 24 hours. Some studies, however, have shown that combined ECPs can be effective on day 4 and 5 after unprotected intercourse and may even be as effective when taken within the first 72 hours. Based on these findings, 72 hours should *not* be used as an absolute time limit for initiating ECPs.
Side Effects
Nausea and vomiting are the most common side effects of combined ECPs. A dose of anti-nausea medicine meclizine significantly reduces the risk of nausea and vomiting--but it also increases the risk of drowsiness. A dose is two 25 mg tablets taken one hour before taking combined ECPs. Whether or not to routinely provide such anti-nausea medication is a decision each program must make based on available resources; meclizine is not routinely provided in the United States. Evidence shows that taking the EC pills with food does not reduce the incidence of nausea and vomiting. The dose should be repeated only if the woman vomits within the first two hours after taking the pills.
The incidence of nausea and vomiting is lower with progestin-only ECPs as compared to combined ECPs. The incidence of nausea is 50 percent lower and vomiting is 70 percent less than with ECPs.
Safety of Combined and Progestin-Only ECPs
Almost all women can safely use combined and progestin-only ECPs; there are no evidence-based contraindications for either one. Given the very short duration of exposure and low total hormone content, combined ECP treatment can be considered safe even for women who would ordinarily be cautioned against the use of COCs for ongoing contraception. According to the World Health Organization, confirmed pregnancy is the only contraindication to combined ECPs, simply because ECPs will not work if a woman is pregnant. Nevertheless, some sources, such as the Faculty of Family Planning and Reproductive Health Care (UK), also include migraine and past history of thromboembolism as relative contraindications and the Planned Parenthood Federation of America lists suspicion of or confirmed pregnancy as a contraindication for combined ECPs. The manufacturers of combined ECPs, such as Preven, are even more cautious and include all the contraindications of COCs in the prescribing information. Plan B, the progestin-only ECP, lists only known or suspected pregnancy as a major contraindication, however.
It is also important to note that neither combined nor progestin-only ECPs have been demonstrated to disrupt a pregnancy or harm a fetus if given after pregnancy is already established. Therefore, EC should not be denied to a women based on a concern that she may already be pregnant, nor should pelvic examination or lab testing be required to rule out pregnancy before administering ECPs.
Finally, although repeated use of ECPs is safe, they are not recommended for routine use as a contraceptive method. Failure rates for ECPs are calculated based on a single use; correct use of a regular contraceptive would result in higher rates of effectiveness. The fact that ECPs do not provide any protection against sexually transmitted diseases (STDs) or HIV, is another strong argument against their routine use.
Beginning Contraception after EC
Condoms, spermicides, and the diaphragm can be started immediately after taking the second dose of ECPs, whereas
Norplant(r) and IUDs should be started after the next menses and a backup method should be used until menses. COCs, Lunelle(r)(a monthly injectable that will be covered in a later session summary) and Depo-Provera(r) can be started the next day after the second dose of ECP; it is not necessary to wait until the client menstruates. A backup method should be used for 7 days.
Last month the following topics were reviewed:
Next month, look for a continuation on the EC update.
For additional information on any of these topics, contact Lois Schaefer at lschaefer@jhpiego.net.