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Women in Europe are being warned the morning-after pill might not work if they weigh more than 165 lbs, but it's not yet clear whether warnings will be issued on the same products in Canada.

HRA Pharma will be issuing warnings in NorLevo emergency contraception after a 2011 study found the drug, called levonorgestrel, loses some of its efficiency if a woman weighs more than 165 lbs, and does not work at all for women who weigh 176 lbs.

In a statement sent to QMI Agency, HRA Pharma Erin Gainer CEO said further analysis by the company confirmed the study's results.

Bayer Canada, which distributes NorLevo in Canada, said HRA Pharma holds the "product's market authorization" and it's up to them to update the product's efficacy and label.

"Bayer has been advised that HRA Pharma and its acting agent (SPharm) are communicating with Health Canada on this issue," a company statement sent to QMI Agency said.

Teva, which makes a similar emergency contraceptive marketed as Plan B, has not yet responded to a request for comment.

Paladin Labs vice-president of Scientific Affairs Patrice Larose said his Montreal-based company is the Canadian distributor and marketer of Plan B, and would not be involved in adding any warning labels to the medication.

Health Canada is aware of the label change in Europe, spokeswoman Leslie Meerburg said in an email.

"Health Canada is assessing the available data on the effectiveness of this product, and will take appropriate action if required, such as working with the manufacturer to update the product labelling and notifying healthcare professionals and consumers of this change."