The health agency has completed a review of the Pfizer drug after evaluating data from a quit-smoking clinical trial involving 700 smokers with cardiovascular disease. Approximately half of the participants in the trial received Champix, while 350 received a placebo.
While a "slightly increased number" of Champix users in the trial experienced "serious heart-related events," Health Canada says the study wasn't adequately designed to test the cardiovascular safety of drug.
"The small study size combined with other study design weaknesses make it impossible to draw conclusions based on these data," Health Canada said in a release.
"The possibility of an increased risk of heart attack or stroke in patients with cardiovascular disease can neither be confirmed nor ruled out at this time."
The updated labelling includes a more detailed description of the study findings and precautions for patients with respect to cardiovascular safety.
Health Canada says it will continue to evaluate new data on the cardiovascular safety of Champix as it becomes available. The agency says it will take appropriate action if new safety information is identified.
Champix is the brand name for varenicline tartrate, and is known as Chantix in the U.S. The prescription drug is used in combination with counselling to help patients quit smoking.