Do emergency contraceptives work for obese women?

Emergency contraceptives, also known as the ‘morning after pill,’ show little to no effectiveness in women who are 165 pounds or heavier. The discovery was made fortuitously by HRA Pharma, the French makers of the emergency contraceptive Norlevo. As a result, that product will bear a related warning label starting in 2014. For those unfamiliar with Norlevo, it is a LNG EC, or levonorgestrel emergency contraceptive. In other words, it is the same as Plan B One Step and its generic versions.
The notion that the effectiveness of emergency contraceptives is inversely proportional to the user’s weight is not new, though. A 2011 study by University of Edinburgh reproductive medicine expert Anna Glasier found that overweight women who take emergency contraceptives are three times  more likely to become pregnant than women with a normal weight. The risk was increased even further when they took levonorgestrel pills. Separate research has also linked extra weight to oral contraceptive failure. The reason may be that this type of medication takes more time to achieve normal concentration levels in the blood of overweight women, according to a 2009 study published in the journal Contraception. Nevertheless, this is probably the first time that a drug label will actually be changed.

HR Pharma promptly informed European health authorities of their finding, and a label change has already been approved, though it will take a few more months before Norlevo-buying countries are supplied with the new packaging. On our side of the pond, the FDA is looking into the available scientific data, which includes the HR Pharma research that triggered the label change. If the federal agency deems it necessary for brand name Plan B to start including a warning, that would enable generic versions Next Choice One Dose and My Way to do so as well.   
In general, levonorgestrel EC’s have approximately 50% effectiveness in preventing expected pregnancies. Moreover, they are readily accessible over the counter, and without a prescription. In light of this experts say that between a less effective drug and nothing, women –whether heavy or not- should choose the former. Obese women are also recommended to resort to an ulipristal acetate emergency contraceptive, which is slightly less affected by weight, or use a copper intrauterine device, which a doctor can insert within five days after unprotected sex. Speaking of which, the best way to prevent an unwanted pregnancy is the correct and consistent use of a birth control method.