A French contraceptive maker says it will begin warning women that its morning-after pill is ineffective when taken by women who weigh more than 176 pounds.
HRA Pharma head of women's health Frederique Welgryn told The Associated Press that the warning is the result of a 2011 study of levonorgestrel, the active compound in its Norlevo emergency contraceptive, and other pills like the Plan B One-Step.
The new warning also says the drug's efficacy is reduced in women who weigh more than 165 pounds.
HRA markets Norlevo in about 50 countries worldwide, including Canada.
It began marketing the pill in France in 1999 and now sells about 1.5 million doses per year there. It will begin printing the warning on packaging in the first half of 2014.
Levonorgestrel is also used in other emergency contraceptives approved for use in Canada.