In its recently released decision in Charlton v. Abbott Laboratories, Ltd., the British Columbia Court of Appeal overturned the certification of a pharmaceutical products liability class action lawsuit. In doing so, the Court drew upon the test of whether there was evidence of a workable methodology of establishing harm on a class wide basis originally developed in indirect purchaser price fixing cases. In its decision, the Court determined that the plaintiffs had failed to introduce evidence of the availability of a methodology to prove general causation and that this was fatal to the certification of the action.
The action was originally certified on the basis of two central claims – the drug in question (Sibutramine) caused or contributed to heart attacks, strokes, and arrhythmia and the propensity of the drug to injure outweighed the value of its use. Justice Johnston of the B.C. Supreme Court certified the action in 2013 making scant reference to the scientific evidence before the Court and commenting that the defendants were proposing an inappropriate weighing of the evidence.
Sibutramine was originally developed as an antidepressant. While on the market, the manufacturer concluded that it served to suppress appetite and sought and obtained approval for its use as a weight loss drug by Health Canada in 2000. A clinical trial (SCOUT Study) conducted between 2003 and 2009 suggested that the drug's use was associated with an increased risk of cardiovascular events when used by patients with pre-existing heart problems. The drug was withdrawn from the market in 2010.
The plaintiffs' expert evidence concluded that Sibutramine caused an increase in heart rate and blood pressure and that in susceptible individuals, this could provoke cardiac arrhythmias. The increase in heart rate and blood pressure was attributed to an inhibition of reuptake of norepinephrine, a neurotransmitter. For their part, the defendants' experts concentrated on the limitations of the SCOUT Study pointing out that its results could not be extrapolated from patients with pre-existing conditions to asymptomatic patients and that the drug's label and product monograph had warned against prescribing the drug to patients with pre-existing cardiac conditions.
The Court of Appeal reviewed the law concerning the "some basis in fact" requirement noting that the Supreme Court in Microsoft had rejected the suggestion that the plaintiffs must meet their evidentiary burden on a balance of probabilities. Focusing on the issues of commonality and preferability however, the Court concluded that the plaintiffs had not met their burden because they had failed to adduce any evidence of the existence of a method of establishing general causation for the class. The epidemiological evidence that was available in the form of the SCOUT Study only established general causation for the very group the drug was not to be prescribed for – those with pre-existing cardiac conditions. Looked at from the perspective of commonality, the lack of evidence of general causation meant that the plaintiffs had not met their burden of some basis in fact to establish their ability to prove general causation. Looked at from the perspective of preferability, the Court noted that this requirement included an assessment of whether a resolution of the common issues would significantly advance the litigation.
The Court Found:
The evidence before the certification judge was that the question of whether Sibutramine causes or contributes to heart attacks, strokes, and arrhythmia on a class-wide basis is incapable of resolution. There is no evidence of a methodology for establishing that the class as a whole, as opposed to those who were wrongly prescribed Sibutramine despite a history of disease, was affected or put at risk by its use of Sibutramine.
Drawing on Ontario authorities, the Court held that where questions relating to causation or damages are proposed as common issues, the plaintiff must demonstrate through the evidence that there is a workable method for determining those issues on a class wide basis. The Court distinguished its previous decision in Stanway on the basis that in that case, the plaintiffs had lead evidence in the form of the results of a large clinical study of a causal connection between estrogen – progestin therapy and the risk of breast cancer.
The question that we are left with continues to be what standard of proof is required to establish some basis in fact in cases involving general causation. Clearly evidence of a large clinical study, such as that relied on in Stanway, would meet the same basis in fact requirement. Equally clear, is that the absence of any epidemiological evidence to suggest the risk of harm on a class wide basis would not. What is unknown, is the fate of cases that fall between these two extremes and whether defendants, armed with the decision in Charlton, will now focus their efforts on seeking to exclude or undermine evidence related to general causation and whether Canadian courts will now have to grapple seriously with concepts such as statistical significance, power modeling and relative risk at the class action certification stage.
 Charlton v. Abbott Laboratories, Ltd., 2015 BCCA 26 CanLII.
 Charlton v. Abbott Laboratories, Ltd., 2013 BCSC 1712 CanLII.
 Pro-Sys Consultants Ltd. v. Microsoft Corporation, 2013 SCC 57 CanLII.
 In class action litigation, general causation is frequently separated from individual causation with the former to be determined at a common issues trial and the latter at individual trials. General causation refers to the product's propensity to injure whereas individual causation refers to its affect on a specific individual.
 Singer v. Schering-Plough Canada Inc., 2010 ONSC 42 CanLII and Chadha v. Bayer Inc., 2003 CanLII 35843.