12/01/2013 06:00 EST | Updated 01/31/2014 05:59 EST

Morning-after pill maker's weight warning raises questions

A French drug maker's warning that its morning-after pill may be ineffective in women who are overweight has Canadian doctors fielding calls. 
This week, HRA Pharma announced it will update labels on its packages of Norlevo to say the efficacy is reduced in women who weigh more than 165 pounds and the medication is ineffective in women who weigh more than 176 pounds. 

In Canada, Plan B and three other emergency contraceptives contain the same active ingredient, levonorgestrel, as the European product, Health Canada said. The products are available over-the-counter.
The European warning is based on a 2011 study that found the morning-after pill was less effective on overweight women compared with other women, said Dr. Wendy Norman, a family physician at the University of British Columbia.  
"I would say categorically that around the world, experts don't feel that there's evidence that this will not work," Norman said. "It was a precautionary move on the part of the manufacturer." 
At Toronto's Planned Parenthood, Dr. Aarti Kapoor is giving a similar message to women asking her questions.  
"I would caution women to take the information in stride, definitely talk to their physician, but don't jump to the conclusion that this pill is completely ineffective," Kapoor said. 
Ideally, the morning-after pill should be taken within 72 hours of unprotected sex, doctors recommend. 
The Society of Obstetricians and Gynecologists of Canada notes that the copper IUD can also be used as an emergency contraceptive up to seven days after unprotected sex and is very effective regardless of a woman’s weight.

The morning-after pill is cheaper than a copper IUD and easier for women to get their hands on, Kapoor said.  
Health Canada said it is assessing all available data on the effectiveness of the product and will take appropriate action if required, such as working with the manufacturer to update the product labelling. The department said its analysis taken into account factors such as the pattern of use of the drug in Canada and prescribing practices.