Intrauterine devices (IUDs) and the etonogestrel implant are the most effective reversible contraceptive methods available. Hormonal oral contraceptives, patches, rings, and injectables are also highly effective in preventing pregnancy. When used alone, barrier and fertility-based methods generally have higher failure rates than other methods.

Implants, intrauterine devices (IUDs), and sterilization are the most effective contraceptive methods available. Pills, patches, rings, and injectables, when used correctly, are also highly effective in preventing pregnancy. Barrier and fertility-based methods have the highest rates of failure.

The progestin levonorgestrel is available over the counter for emergency contraception as two 0.75-mg tablets taken 12 hours apart (generic formulations of Plan B) and as a single 1.5-mg tablet taken once (Plan B One-Step, and generics). A third emergency contraceptive, ulipristal (Ella – Watson), is available with a prescription.1 It appears that, pursuant to a court order, Plan B One-Step (but not the generic products), which was previously available over the counter from a pharmacist only for women 17 years and older, will now be available directly from pharmacy shelves with no age restrictions.

EMERGENCY CONTRACEPTION — Currently used hormonal methods of emergency contraception, which apparently mainly prevent or delay ovulation, can prevent 50-80% of pregnancies.2 They should be started as soon as possible within 72 hours after unprotected intercourse. One study found that taking levonorgestrel as late as 120 hours after unprotected intercourse could still be effective.3

Many oral contraceptives can be used in doses suitable for emergency contraception. All are recommended for use in 2 doses 12 hours apart, but given the effectiveness of a single dose of levonorgestrel 1.5 mg in Plan B One-Step, taking the tablets all at once might be an option. Patients who vomit within 1 hour of administration can repeat the dose. A copper IUD inserted within 5 days after intercourse can also provide emergency contraception.

ADVERSE EFFECTS — Nausea and vomiting occur less frequently with levonorgestrel alone than with estrogen-progestin combinations. Headache, abdominal pain and breast tenderness have been reported with either progestin-only or combination oral contraceptives. No fetal malformations caused by unsuccessful use of hormones for emergency contraception have been reported.

1. Ella: a new emergency contraceptive. Med Lett Drugs Ther 2011; 53:3.

2. DT Baird. Emergency contraception: how does it work? Reprod Biomed Online 2009; 18 suppl 1:32.

3. H von Hertzen et al. Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: a WHO multicentre randomised trial. Lancet 2002; 360:1803.

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The FDA has approved the use of ulipristal acetate (ella – Watson) as an emergency contraceptive that can be taken up to 5 days after unprotected intercourse. It is available only by prescription.