Summary Safety Review - Combined Hormonal Birth Control Products - Evaluating effectiveness when used by women who are obese
Review decision
A Summary Safety Review complements other safety related information to help Canadians make informed decisions about their use of health products. Each summary outlines what was assessed in Health Canada’s review, what was found and what action was taken by Health Canada, if any.
Issued: 2015-07-23
Product
Combined Hormonal Birth Control Products
Potential Safety Issue
Risk of decreased effectiveness of combined hormonal birth control products when used by women who are obese
Overview
Use in Canada
- Combined hormonal birth control products are used to prevent pregnancy. These products are available as pills, skin patches and vaginal rings. The pill is the most common form.
- Combined hormonal birth control products are widely used in Canada. In 2014, they were among the top 100 most prescribed drugs in Canada2.
Safety Review Findings
- Until May 31, 2014, Health Canada received 8 reports of pregnancy associated with combined hormonal birth control products with information to confirm obesity3. The review of these reports was limited by several factors, including not being able to confirm pre-pregnancy weight and compliance with the birth control product as directed. Therefore, these reports could not show an association between obesity and pregnancy occurring while taking combined hormonal birth control products.
- Some recent studies suggested that obese women may have lower blood levels of birth control hormones when compared to non-obese women. However, the studies did not demonstrate conclusive evidence that this leads to a decrease in effectiveness in obese women using combined hormonal birth control products. One study suggested that the patch form may be less effective in women with a body weight higher than 90 kg (198 pounds). This information is already found in the Canadian prescribing information for the patch.
- A majority of other studies on the effectiveness of combined hormonal birth control products also did not show conclusive evidence of a decreased effectiveness in obese women. Many of the studies had limitations of not being able to confirm the proper use of the pill and only included a small number of obese women in the studies.
- In 2007, the United States Food and Drug Administration's Advisory Committee for Reproductive Health Drugs recommended that the entry criteria of studies should include women with higher body mass indexes.
Conclusions and actions
- The safety review found no conclusive evidence to show a higher risk of pregnancy in obese women compared to non-obese women when using combined hormonal birth control products.
- Health Canada is requiring that the labelling of newly marketed combined hormonal birth control products in Canada contain information regarding the weight of the people studied including BMI. This information is not required for older combined hormonal birth control products as it may not be available (for example, BMI may not have been collected during the clinical trials). This information is being added for specificity to provide further context on the parameters of the studies even though, at this time, the current safety review did not find a higher risk of pregnancy in obese women.
- Health Canada will continue to monitor this safety issue.
Additional information
The analysis that contributed to this safety review included scientific and medical literature, Canadian and international adverse reaction reports and what is known about the use of this drug both in Canada and internationally.
For additional information, contact the Marketed Health Products Directorate.
References
- More information about Body Mass Index is available on Health Canada's Web site.
- IMS utilization data provided by: IMS Health Canada Inc. An external party cannot refer to nor use IMS data, which have been generated by Health Canada, without a Third Party Agreement in place.
- Canadian reports can be accessed through the Canada Vigilance Adverse Reaction Database.