The heart drug Multaq continues to be approved for use in Canada, but Health Canada says reports of its connection to liver damage will be reviewed.

On Friday, the U.S. Food and Drug Administration added new warnings to the label of the Sanofi-Aventis drug after several reports that patients suffered liver damage.

Multaq was approved in July 2009 to treat atrial flutter and atrial fibrillation — irregular heart rhythms that can reduce blood flow and lead to stroke.

Liver toxicity is among the most common drug-related side-effects in a number of medication classes.

Health Canada says that in Canada the drug is not to be used by patients with severe liver problems. It says that should new safety information be identified, it will take appropriate action — including keeping health-care professionals and other Canadians informed.

Up to Oct. 31, Health Canada received 40 adverse reaction reports representing 37 cases (three of the reports were duplicates) with the suspect product being Multaq. It says none of these reports were related to liver damage.

Adverse reaction reports are considered to be suspicions, since a definite cause-and-effect relationship often cannot be determined without additional scientific investigations.

The Canadian Heart and Stroke Foundation website notes that atrial fibrillation (AF) affects about 250,000 Canadians. While it is rare in people under 40, its prevalence increases with age. About three per cent of the population over the age of 45 and six per cent over age 65 have atrial fibrillation. After age 55, the incidence of AF doubles with each decade of life.

Multaq already carries a black-box warning in the U.S., the most severe type, stating the drug can cause severe complications, including death, in people with recent severe heart failure and should not be used by those patients.

Common side-effects of the twice-a-day tablets include:

  • Fatigue.
  • Loss of strength.
  • Diarrhea.
  • Nausea and vomiting.

Sales of the drug in the U.S. alone are estimated at $128 million for 2010.

With files from The Associated Press