A French contraceptive maker said today its morning-after pill is ineffective when taken by women who weigh more than 80 kilograms (176 pounds).
The decision by HRA Pharma follows a publication of results of a study of levonorgestrel, one of the active ingredients in its Norlevo emergency contraceptive, said Frederique Welgryn, HRA Pharma's head of women's health.
Welgryn said that while the results of the study conducted by the Edinburgh University in 2011 were "quite surprising," the last few years have seen "a lot of discussions" about contraceptives' efficacy in overweight or obese patients.
HRA Pharma Chief Executive Erin Gainer estimated that "millions" of women across Europe use emergency contraceptives identical to Norlevo. Gainer declined to give sales figures for Norlevo alone.
Anna Glasier, a lead researcher in the study, said that their research wasn't designed to look specifically at the effect of weight on emergency contraception. She said their study only included about 1,700 women.
"It is not my place to comment as to whether the company's decision to change advice is premature," she said in an email.
She also noted another previous analysis that found there was no solid evidence to show that hormonal contraceptives were less effective in overweight women, but the quality of the studies was low.
Welgryn said a dose of HRA's drug contains 1.5 mg of levonorgestrel, identical to that found in Plan B One-Step, manufactured by Teva Pharmaceuticals, use identical ingredients.
Denise Bradley, a spokeswoman for Teva Pharmaceuticals, declined to comment.
HRA began the process of consulting with French regulators about changing the pill's labelling in 2012 and it has taken until now for Europe's drug regulators to approve the change, Welgryn said.
The new warning also says that the drug's efficacy is reduced in women who weigh more than 75 kilograms (165 pounds), and it is ineffective in women who weigh more than 80 kilograms.
Dr. Diana Mansour, a spokeswoman for Britain's Faculty of Sexual and Reproductive Healthcare, said in overweight and obese women the drug probably gets absorbed into their fat more quickly and doesn't have enough time to work in their bodies.
