A new study is claiming that Pfizer moved the goalposts and issued misleading data when it came to analyses of off-label use of its epilepsy drug Neurontin.

Researchers at the University of California at San Francisco and the Johns Hopkins Bloomberg School of Public Health have presented data, published in the New England Journal of Medicine, on the premise that “there is good evidence of selective outcome reporting in published reports of randomised trials.

Specifically, they examined reporting practices for trials of Neurontin (gabapentin) funded by Pfizer and its Parke-Davis unit for off-label indications (prophylaxis against migraine and treatment of bipolar disorders, neuropathic pain, and nociceptive pain). They compared internal company documents with published reports.

The researchers identified 20 clinical trials for which internal documents were available from Pfizer, 12 of which were reported in publications. For eight of the 12, “the primary outcome defined in the published report differed from that described in the protocol,” they say.

The study notes that “sources of disagreement included the introduction of a new primary outcome (in the case of six trials), failure to distinguish between primary and secondary outcomes (two trials), relegation of primary outcomes to secondary outcomes (two trials), and failure to report one or more protocol-defined primary outcomes (five trials). They argue that studies which presented findings that were not significant for the protocol-defined primary outcome in the internal documents “either were not reported in full or were reported with a changed primary outcome”.

They go on to argue that the primary outcome was changed in the case of five of eight published trials for which statistically significant differences favoring gabapentin were reported. Of the 21 primary outcomes described in the protocols of the published trials, “six were not reported at all and four were reported as secondary outcomes”. Of 28 primary outcomes described in the published reports, 12 were newly introduced.

The researchers conclude that they did indeed find selective outcome reporting for trials of off-label use of gabapentin, adding that “this practice threatens the validity of evidence for the effectiveness of off-label interventions.

Pfizer, which pleaded guilty to criminal charges for off-label promotion of Neurontin in 2004, disputes the report's conclusions, and issued a statement saying that it never ''attempted to mislead the medical community about the effectiveness'' of the drug for certain uses. The company added that “we believe the review suffers from significant bias, insufficient data, poor methodology and cannot pass the threshold of credible scientific research''.