Your Voice

April 1, 2006

Dosing inconsistencies and other questions about emergency contraception

Regarding Drs. Conard's and Gold's informative article "What you need to know about providing emergency contraception" (February 2006), I noted that the dosing instructions for levonorgestrel (Plan B) in the "Guide for Patients" differed from what is provided by the drug's manufacturer. I confirmed this observation with a telephone call to the company: The first pill should be taken as soon as possible, at a logical time of day; the second should be taken exactly 12 hours later. Please advise.

Margaret Schmandt, MDSt. Louis, Mo.

Drs. Conard and Gold summarize the proposed mechanisms by which oral EC regimens work. Included in the possibilities are "causing impairment of sperm function or altered transport of sperm, egg, or embryo or by altering the endometrial lining." The authors answer the question, "If EC is taken when a woman is already pregnant, will it cause a miscarriage or birth defects?," with "No."

R. Michael Green, MDKnoxville, Tenn.

Authors' reply: Dr. Schmandt rightly observes that the Plan B package information recommends a dosing regimen in which the first tablet is taken as soon as possible after unprotected or underprotected intercourse, and the second tablet is taken 12 hours later. This is also the Food and Drug Administration (FDA) approved dosing regimen. However, there are sound data to support the protocol for emergency contraception (EC) that we describe in the article, in which the patient takes both tablets together, as soon as possible after unprotected or underprotected intercourse.

In one study, women were given the Yuzpe regimen (containing both estrogen and levonorgestrel) and their use was analyzed by timing of initiation; receiving it within 72 hours (n =131) or between 72 and 120 hours (n =169). The observed pregnancy rate was 1.1% for both groups, and the effectiveness was 87% for both groups. The chi-square tests were significant for both groups (P<.5) and observed pregnancy rates were lower than expected pregnancy rates. This shows that the Yuzpe regimen is effective after 72 hours.1

A second study of 111 women assessed the effect of extending the 72-hour time limit for EC to 120 hours; subjects who presented 72 to 120 hours after unprotected intercourse were offered the standard Yuzpe regimen of EC when they refused intrauterine device (IUD) insertion. Perfect use (1.9%) and typical use (3.6%) failure rates were low, and did not differ statistically from failure rates for the standard Yuzpe regimen when it was taken within 72 hours.2

A third study compared the efficacy of a single 10-mg dose of mifepristone (not available for EC in the US), two 0.75-mg doses of levonorgestrel given 12 hours apart (Plan B packaging directions) and a single 1.5-mg dose of levonorgestrel (the directions we recommended in our article) given within 120 hours of unprotected intercourse. There were no significant differences in the pregnancy rate between groups. Side effects were mild, and did not differ significantly between groups.3

Because good evidence supports the use of Plan B by giving both tablets at once, and because it is easier for patients of all ages to remember to take only one dose of medication instead of two, the American Academy of Pediatrics, the Society for Adolescent Medicine, and the American College of Obstetrics and Gynecology all recommend this simplified dosing regimen for adolescents.4-6 In addition, a patient who takes the first dose at 3 pm must ideally take the second dose at 3 am, which may prove difficult. We give patients the "Guide for Patients" that accompanied our article, and explain that the directions we are providing are different from those on the package.