Decision Excluding Causation Theory in Rezulin MDL Impacts Other Cases

In an important recent Daubert decision, Judge Lewis A. Kaplan of the Southern District of New York ruled that plaintiffs in the Rezulin multidistrict litigation may not rely on proposed expert opinion testimony that the medication can cause liver injury to a patient who did not experience markedly abnormal liver enzymes while on therapy. In Re Rezulin Products Liability Litigation, MDL 1348, 2005 U.S. Dist. LEXIS 3790 (SDNY Mar. 14, 2005), hereinafter (“In Re Rezulin”). Apart from its profound implications for the Rezulin litigation, the decision has far-reaching significance for pharmaceutical and toxic tort product liability cases.

Rezulin was a prescription medication used to treat type 2 diabetes. Like all medications, Rezulin had risks as well as benefits. In rare cases, some people who took Rezulin had an acute, idiosyncratic reaction to the medication, about which the FDA-approved label specifically warned. The hallmark of this reaction is a release of liver enzymes into the bloodstream, which is detectable by standard laboratory tests. Plaintiffs’ experts proffered the novel theory that Rezulin could cause an injury without the release of enzymes into the bloodstream. Thus, they posited a theory of invisible and undetectable liver injuries, so that any liver disease diagnosed after a patient took Rezulin could be attributed to Rezulin (the “silent injury” theory).