Morning-after pill: not so effective for some women? Photo: SUPPLIED ZZZ
An investigation by a French pharmaceutical company has discovered that the morning-after pill may not work for women weighing more than 80 kilos, and that it begins to lose its effectiveness for individuals who weigh over 75 kilos. In light of the news, HRA Pharma, the European manufacturer of emergency contraceptive NorLevo, stated that it will now include a warning regarding weight limitations in every packet sold from the first half of 2014, according to a report by Mother Jones. Levonorgestrel, NorLevo's active ingredient, is found in similar progestogen-only contraceptives such as Postinor and Levonelle.
HRA Parma began looking into claims that their drug lost efficacy for women with a higher body mass index following the release of a study by Anna Glasier, an expert in reproductive medicine at the University of Edinburgh. After finding evidence to support Glasier's research they decided to update packaging information to read that the drug is not recommended for those over 75 kilos. Data released by the Australia Bureau of Statistics last year shows that the average weight for women over the age of 18 is 71.1 kilos. "When we became aware that there appeared to be an impact on efficacy, we felt it was our ethical duty as a drug manufacturer to report it and be transparent," said HRA Pharma chief executive Erin Gainer.
The revelation has caused a stir. Within 11 hours of the release of the initial report the US Food and Drug Administration stated that it had begun reviewing evidence to see if similar emergency contraceptive drugs on the US market would be made to change their warning labels. "Both brand and generic drug manufacturers have an ongoing obligation to ensure their product labelling is accurate and up to date," said FDA spokeswoman Erica Jefferson. "When new information becomes available that causes information in drug product labelling to be inaccurate, both brand and generic drug application holders must take steps to change the content of their product labelling."
At this time there is no clinical evidence to suggest that taking increased amounts of levonorgestrel will improve efficacy, and the company recommended that women weighing more than 75 kilos speak with their doctors regarding alternative options. "A dose increase of levonorgestrel is not proven to be a solution for this problem," said HRA Pharma spokeswoman Karina Gajek.
“Women with higher weight are advised to discuss alternative emergency contraceptive options with their physician: IUD or alternative oral emergency contraceptive."
While it is unclear why the drug is less effective for larger women - one theory is “that body weight affects the way drugs are metabolised” - Glasier's study found that they are three times more likely to fall pregnant after taking levonorgestrel than individuals with a lower body mass index. However, she believes that women over 75 kilos are better off taking the drug if it is their only available option. "You are probably better to take LNG-EC [levonorgestrel emergency contraceptives] after unprotected sex than just to leave it to chance even if you are obese,” she said.
It's a sentiment echoed by Family Planning NSW's medical education co-ordinator, Dr. Mary Stewart. She says that options for emergency contraception are limited in Australia and recommends that women still take pills containing levonorgestrel or consider copper IUDs. “In Australia the only emergency contraceptive pill we have is the levonorgestrel pill, with various brands available. Australia does not have ulipristal acetate, which is a more effective alternative. The copper IUD is actually a more effective form of emergency contraception and then offers ongoing contraception. However, the access to a copper IUD in the five-day time frame can be extremely difficult,” she said.
“My understanding is that there is insufficient evidence about efficacy at higher BMIs for levonorgestrel-EC. However, in the absence of an alternative, the emergency contraceptive pill we have, which is extremely safe, is still likely to offer some benefit in preventing an unintended pregnancy and is better than nothing.”