A couple of years ago, researchers exploring the effectiveness of emergency contraception uncovered an interesting thing: that levonorgestrel, which is used in a number of over-the-counter morning-after pills, becomes less effective in women over 165 pounds (75 kilograms) and is almost completely ineffective for women weighing over 177 pounds (80 kilograms). In 2011, they published their results, drawing the attention of a number of pharmaceutical companies that develop emergency birth control. The lead author of the paper, Anna Glasier, noted that the study wasn’t created to look at weight specifically, suggesting that more studies need to be made before efficacy can be determined in heavier women.
Nevertheless, French company HRA Pharma, which manufactures Norlevo, an emergency contraceptive that uses levonorgestrel, is changing its labeling on its emergency contraceptives. The company began discussing this with European regulating bodies at the end of 2012, after the Edinburgh University study led them to review other clinical data. European drug regulators approved the change on November 10 of this year, according to Frederique Welgryn, HRA Pharma’s head of women’s health.
Starting in 2014, labeling will appear inside every box of Norlevo distributed in Europe, warning: “Studies suggest that Norlevo is less effective in women weighing [165 pounds] or more and not effective in women weighing [176 pounds] or more” and that the emergency contraceptive is not recommended “if you weigh [165 pounds] or more.”
Many other emergency contraceptives use levonorgestrel, including Levonelle in the United Kingdom, and Plan B One-Step, Next Choice One Dose, and My Way in the United States. In the United States, levonorgestrel morning-after pills are the only emergency contraception that are available to women without a prescription. Of these, Plan B One-Step is the only one available to women of all ages without a prescription.
Survey data from 2007 to 2010 show that American women over 20 years of age average 166 pounds or more — heavier than the weight required for levonorgestrel to be effective as a means of emergency birth control.
Unfortunately, American manufacturers of brand name emergency contraception have made no move to change their own labeling, and as Mother Jones notes, “Because the Food and Drug Administration prohibits generic drug manufacturers from changing product information unless the brand name manufacturer makes a change, companies that manufacture generic versions of Plan B One-Step cannot update their packaging information unless Teva Pharmaceutical Industries, the exclusive manufacturer of Plan B One-Step, acts first.”
The Food and Drug Administration, meanwhile, has reached out saying that they are working to determine whether they will require emergency manufacturers to change their labels.
It is not known why weight affects efficacy of these pills. Dr. Diana Mansour, a spokeswoman for Britain’s Faculty of Sexual and Reproductive Healthcare, told the Guardian that the drug probably gets absorbed into fat more quickly in overweight women and doesn’t have enough time to work. That said, Karina Gajek, a spokeswoman for HRA Pharma, indicated that increasing the dosage of levonorgestrel is not proven as a solution for overweight women.
Gajek suggests intrauterine device (IUD), which works no matter the weight, or an alternative emergency contraceptive. Ella, which uses ulipristal acetate, has shown in clinical trials to be more effective for overweight women (though it too starts to lose effectiveness at a BMI of 35.1 or higher). For other emergency contraceptive options, check out Bedsider.org and talk with your doctor. If you don’t have a doctor, check your local Planned Parenthood. Drugstores may have small walk-in clinics on premises; CVS has the Minute Clinic in various states, for instance.