Diminution de l'efficacité du Plan B chez les femmes de plus de 165 livres

They found that the risk of pregnancy was more than three times higher in obese women, defined as a body mass index of 30 kg/m or higher) when compared to those with a normal body mass index. In women who were considered overweight (defined as a body mass index between 25 and 29.9 kg/m), the risk of pregnancy was 1.5 times greater. 

The new NorLevo packaging in Europe will include a statement stating that studies suggest NorLevo is less effective in women over ≥165 pounds (75 kg) and not effective in women over ≥175 pounds (80 kg). The Society of Obstetricians and Gynaecologists of Canada released a statement highlighting the potential for emergency contraceptive failure in overweight women, and suggests that these women should see their health care provider for advice. 

 There is no information regarding the efficacy or safety of levonorgestrel doses greater than 1.5 mg for emergency contraception. In addition, it is likely that the incidence of vomiting would be higher with higher levonorgestrel doses. At this time, higher doses of levonorgestrel cannot be routinely recommended for overweight women.

Consequently, insertion of a copper IUD within five days (seven days per Canadian guidelines) of unprotected intercourse is the best option. However, because emergency contraception is the last chance to prevent pregnancy, in a woman who refuses an IUD,levonorgestrel or ulipristal should be offered as less effective alternatives. 
Au Canada, l'ulipristal (Fibristal) est seulement disponible en 5mg et indiqué pour le fibrome utérin, mais aux États-Unis, il est disponible en 30mg pour la contraception orale d'urgence. 

Tiré du Canadian Pharmacist's Letter, janvier 2014
et de Vigilance