Saskatchewan Court of Appeal confirms that “General Causation” need not be certified as a common issue in failure to warn class actions

In Bayer Inc v Tluchak Estate, the Saskatchewan Court of Queen’s Bench certified a class action involving the prescription anticoagulant rivaroxaban, which is marketed in Canada under the brand name Xarelto. The defendants (collectively, “Bayer”) sought leave to appeal, arguing that the Chambers judge erred by certifying a common issue regarding an alleged failure to warn of bleeding risks without first certifying a common issue on general causation. The Saskatchewan Court of Appeal denied leave to appeal, finding that the certification of a general causation common issue is not a necessary precondition to the certification of a failure to warn common issue.  


The representative plaintiff sought to certify a class action on behalf of all Canadian residents who were prescribed Xarelto in Canada, and related individuals who may make a claim under family compensation legislation. The representative plaintiff alleged that Bayer: (i) breached its duty of care by marketing Xarelto at all, or by failing to indicate it was for a narrower population (the “marketing claim”); and, (ii) negligently failed to provide a clear, current or complete warning explaining the risk of bleeding, how to reduce the risk and how to manage bleeding (the “negligent warning claim”).

The Chambers judge certified the negligent warning claim, but refused to certify the marketing claim.

The leave decision

Bayer sought leave to appeal the certification order. It argued, among other things, that the Chambers judge erred in certifying the negligent warning claim without first certifying a general causation common issue.

The Court of Appeal denied leave to appeal, concluding that the proposed appeal: (i) was not of overarching importance to the proceedings; and, (ii) did not add anything to class actions practice or the administration of justice generally.

While the Court acknowledged that pharmaceutical class actions often include common issues relating to general causation, it concluded that the certification of a general causation common issue is not necessary in every duty to warn analysis, particularly where – as here – the general propensity of the product to injure is acknowledged by the manufacturer.

Furthermore, the Court held that it is not necessary to certify a general causation common issue as long as the failure to warn common issue encompasses a general causation element. In this case, the Court found that the Chambers judge “operated under the presumption” that he was certifying a common issue that included the general causation step. In other words, at the common issues trial, the details of the general causation issue would have to be proven in order to determine whether there was a failure to warn.

Bayer also argued that the Chambers judge erred by certifying the negligent warning claim without requiring a class wide methodology for determining general causation. The Court of Appeal rejected this argument, finding that there is no need to have a workable methodology for a common issue that is not certified.

Lessons learned

The decision to deny leave in Bayer affirms the low threshold for certification, particularly in the context of product liability claims. The Court of Appeal repeatedly noted that the certification stage is not the place to perform an in-depth analysis of the merits of the case, and that the test for leave to appeal must be considered in this context.

As a result of this low threshold, a representative plaintiff may be allowed to certify aspects of a proposed pharmaceutical class action, even in cases where that plaintiff cannot demonstrate a workable methodology to address general causation issues.

More generally, the case highlights the fact the certified common issues need not, in and of themselves, be dispositive of all aspects of the asserted claims. At the same time, the courts appear willing to take an expansive view of those common issues that are certified, to the point of “presuming” that the constituent elements of a particular claim can be subsumed within the broader articulation of the common issues.