Canadian regulators have approved AstraZeneca's key new heart drug Brilinta, boosting prospects for a product whose future in North America is uncertain.

The green light from Health Canada means the medicine is now approved in 33 countries, including in the European Union under the trade name Brilique.

Despite the growing tally of approvals, Brilinta's prospects in the key US market are under a cloud because American patients taking it in a pivotal clinical trial appeared to do worse than those on Plavix. 

Astra's drug is viewed as a potential multibillion-dollar seller that would compete with Sanofi and Bristol-Myers Squibb's  Plavix, but only if doctors are convinced it will work better.
Plavix, the world's second- biggest selling drug, brings in some $9 billion a year.

There has been speculation that the US Food and Drug Administration (FDA) may ask for more evidence of the drug's effectiveness in US patients before approving it.

The FDA is due to make an approval decision on the drug, considered the company's most important new product, by July 20. - Reuters