How They Work; Pros and Cons
Hormonal methods contain ethinylestradiol (EE) and a progestin (Yuzpe method) or
A progestin alone (Plan B® or NorLevo®).
The non-hormonal method is a copper intrauterine device (copper IUD).
Mechanism of Action
Many mechanisms of action might be involved. Hormonal methods may interfere with the ovulation process, the luteal phase length and implantation.
The copper IUD induces a foreign body reaction and likely interrupts fertilization and blocks implantation.
Yuzpe method should ideally be used within 72 hours of an episode of unprotected act of intercourse. There is evidence of benefit up to 5 days after unprotected sex. In this method two tablets of Ovral®, each containing 0.05mg of EE and 0.25mg of levonorgestrel, are administered at once, followed by two tablets 12 hours later. Any combined oral contraceptives can be substituted for Ovral® as long as the same doses of EE and progestin are used. Alternatives are listed:
| ||Pills/Dose||EE ,|
Alternative dosing of available oral contraceptives when used for emergency contraception.
Plan B® or NorLevo® should ideally be used within 72 hours of an episode of unprotected intercourse. There is evidence of benefit up to 5 days after unprotected sex. In this method one tablet of 0.75mg levonorgestrel is administered initially, followed by a second tablet 12 hours later OR the two 0.75 mg tablets are taken together in one dose.
The copper IUD can be inserted within 7 days of a single unprotected act of intercourse. This is the best option available to a woman who presents 3 to 7 days following unprotected intercourse.
- Although each of these methods is effective for preventing unplanned pregnancy, the progestin-only methods (Plan B® or NorLevo®) are the preferred hormonal options due to the highest success rate, low side effect profile and availability without a prescription.
- The copper IUD may be used up to 7 days after intercourse.
- Nausea and vomiting are common side effects following hormonal emergency contraception particularly the Yuzpe method. An anti-nauseant before each dose may reduce the risk of vomiting. Vomiting, if it occurs, is usually after peak systemic absorption has been achieved. If vomiting occurs within the first hour of ingestion the dose should be repeated.
- Hormonal emergency contraception may delay the next menses by one week.
- Emergency contraception is intended for occasional use, when primary means of contraception fail. Regular use of a contraceptive method is preferred.
- Emergency contraception does not protect against sexually transmitted infections (STI).
- The copper IUD must be inserted by a health-care professional.
Hormonal methods of emergency contraception prevent between 75 to 95 percent of pregnancies if administered within 24 hours. The success rate however, decreases with each 12-hour delay. Every effort should be made to administer the medication as soon as possible.
The copper IUD is also a highly effective form of emergency contraception, with a 1% failure rate.
1. Known pregnancy (only because emergency contraception does not have any effect on an established pregnancy)
1. The Yuzpe method should ideally be avoided in women with absolute contraindications to estrogen. The progestin-only options are the preferred options.
2. The copper IUD should preferably only be inserted in women who would otherwise be a suitable candidate for the IUD. There should be on history of recent pelvic inflammatory disease, low risk for sexually transmitted infection, and no evidence of vaginal or cervical infection.
A pregnancy test should be performed if the woman does not experience normal menstrual bleeding by 21 days after the treatment (28 days if she began using oral contraceptives after taking emergency contraception).
If indicated, a follow-up visit can be made three to four weeks post treatment and can include counseling about the need for regular contraception, testing for STIs (if needed) and education about prevention against sexually transmitted diseases should be offer.