A study of internal company documents suggests that Pfizer altered or omitted unfavorable study findings to expand the market of its epilepsy drug Neurontin's market.

Clinical trials are supposed to answer a specific, predetermined scientific question, but a comparison of Pfizer documents and published studies on Neurontin for conditions other than epilepsy found that eight out of 20 study reports never made it into medical journals. And in eight of the 12 published studies, the primary outcome was changed by Pfizer.

The studies, all funded by Pfizer, showed how the drug worked in people with problems like migraines or pain, which are off-label uses of the drug.