Evidence that the levonorgestrel emergency contraceptive is less effective in overweight women is being reviewed by the Food and Drug Administration, which will determine whether this information should be added to the U.S. labeling of the product.
In November, a warning that Norlevo, which contains 1.5 mg of levonorgestrel, is less effective in women who weigh at least 75 kg (165 pounds) and is not effective in women who weigh more than 80 kg (176 pounds), was added to the label of the product in Europe. No such information is included in the labels of the levonorgestrel emergency contraceptives marketed in the United States. Norlevo, which is not available in the United States, contains the same dose as Plan B One-Step, a 1.5-mg levonorgestrel tablet, available over the counter for women aged 15 years and older in the United States.
Dr. Carolyn Westhoff
In response, "the FDA is currently reviewing the available and related scientific information on this issue, including the publication upon which the Norlevo labeling change was based," an FDA spokesperson said. "The agency will then determine what, if any, labelling changes to approved emergency contraceptives are warranted." The FDA’s approval of Plan B did not include a weight-related assessment of efficacy.
The study, a meta-analysis of randomized studies comparing the efficacy of ulipristal acetate (marketed as ella), and levonorgestrel emergency contraceptives, conducted to identify factors associated with failure of the emergency contraceptives, was published more than 2 years ago. For all emergency contraceptives, the risk of pregnancy was more than three times higher (odds ratio, 3.06) among obese women compared with women with a normal body mass index (BMI). But when investigators looked at specific methods, the risk of pregnancy among obese women was four times higher among those who took levonorgestrel (OR, 4.41) compared with those who used ulipristal (Contraception 2011;84;363-7).
Ulipristal is taken as a single tablet and requires a prescription. Experts in the United States already recommend other emergency contraceptive options, when possible.
Dr. Carolyn Westhoff, professor of obstetrics and gynecology, and of epidemiology, New York–Presbyterian Hospital/Columbia University Medical Center, said she advises clinicians to inform women of any weight that the copper IUD is the most effective form of emergency contraception available. It can be inserted at any time during the cycle, provides ongoing contraceptive protection, and, if indicated, routine screening for chlamydia can be performed at the time of insertion, she pointed out.
After the copper IUD, the most effective emergency contraceptive is ulipristal acetate, which can be prescribed in advance to sexually active women of reproductive age, she added. "While the effectiveness of ella might diminish somewhat with greater weight, that effect is less pronounced," said Dr. Westhoff, who is also the medical adviser to Planned Parenthood Federation of America (PPFA).
"At this point in our understanding, it seems that Plan B should be last choice when providing EC. For women who do not have a relationship to a health care provider, it might be the only choice, but for those women who have a relationship with a clinician, the more effective methods are always preferable," she said.
Planned Parenthood does not recommend Plan B for women with a BMI over 30, according to Karen Shea, director of medical standards at PPFA.
A statement provided by PPFA says that over-the-counter forms of emergency contraception, such as Plan B One-Step, "may not be as effective among women with a BMI of 25 or higher," and points out that "regardless of a woman’s weight, after 3 days, over-the-counter forms diminish in effectiveness."
Generic two-pill formulations of levonorgestrel are also available in the United States.
Dr. Westhoff said she had no relevant financial disclosures. Teva Pharmaceuticals, which markets Plan B One-Step in the United States, did not respond to a request for a comment.