In In re Neurontin Marketing and Sales Practices and Products Liability Litigation, 2011 WL 1048971 (D. Mass. Mar. 18, 2011), over one hundred individuals experienced behavioral disturbances, depression and ultimately suicidal actions, including completed suicide, after their doctors prescribed an anti-epileptic drug, gabapentin. The individuals and their estates’ representatives sued the drug’s manufacturers in the United States District Court for the District of Massachusetts alleging the drug caused the individuals’ injuries and deaths.  

Since 2004, gabapentin has been the subject of a protracted multi-district litigation with two distinct parts: (1) “sales and marketing” actions brought by consumer purchasers and third party payors stemming from an alleged fraudulent offlabel marketing scheme (see October 2010 Foley Hoag Product Liability Update; In re Neurontin Marketing and Sales Practices and Products Liability Litigation, 2010 WL 3169485 (D. Mass. Aug. 10, 2010)); and (2) “products liability” actions, such as this one, alleging injuries resulting from the use of gabapentin. In the latter type of action, plaintiffs bear the burden of establishing both general and specific causation. As explained in the Federal Judicial Center’s Reference Manual on Scientific Evidence, cited by the court, “General causation is established by demonstrating, often through a review of scientific and medical literature, that exposure to a substance can cause a particular disease . . . . Specific, or individual, causation, however, is established by demonstrating that a given exposure is the cause of an individual’s disease . . . .”

In support of their theory of general causation, plaintiffs relied upon a meta-analysis by the United States Food and Drug Administration (“FDA”) of various manufacturers’ clinical trials. The analysis supported an association between one class of anti-epileptic drugs - which included gabapentin and four others - and an elevated risk of suicidal thoughts and behavior short of an actual suicide attempt. Defendants’ expert, however, conducted studies specifically of gabapentin, which were published in a peer-reviewed journal, from which he concluded that, regardless of whether the drug causes an increase in suicidal thoughts or behavior, there was no increased risk of actual suicide attempts. In an unpublished supplemental report, the expert expanded his conclusion, opining the drug did not even increase the risk of suicidal thinking or behavior.

Plaintiffs moved to partially exclude the testimony of defendants’ expert because the methodology of his studies was unreliable. Specifically, plaintiffs argued the expert’s findings should be characterized in terms of “associations” rather than “causal inferences,” and attacked his methodology on the basis that it did not take into account the concomitant effect of certain other drugs taken by the gabapentin patients.

The court denied the motion to exclude defendants’ expert’s testimony despite finding that plaintiffs’ criticisms “undermined” the expert’s opinion. Citing the publication of the expert’s study in a peer-reviewed journal, the court explained that the expert’s opinion was not so fundamentally unsupported that it must be excluded. Instead, the conflicting views of plaintiffs’ and defendants’ experts should be explored through cross-examination and submitted for a jury’s consideration. However, the court did preclude defendants’ expert from testifying that his studies supported any conclusion relating to suicidal thoughts (as discussed in his unpublished supplemental report), as the studies had been specifically limited to the issue of suicide attempts.