Analysis of a dozen studies testing possible new uses for a Pfizer Inc. epilepsy drug found the published results were often fudged, indicating the medicine worked better than internal company documents showed.

According to the report, when a company-funded study's primary finding wasn't favorable, the study authors usually buried that result and found something else positive to highlight, without disclosing the switch.

The documents used in the review were obtained by lawyers suing Pfizer for refunds on prescriptions paid for by insurers and consumers. The lawyers, who are seeking class action status for the cases, claim Pfizer concealed evidence the epilepsy drug Neurontin didn't work for those unapproved uses, including nerve pain, migraines and bipolar disorder.

One of the report's authors is an expert witness for the plaintiffs; another has received fees from the lawyers.

Pfizer disputes the report's conclusions, saying the company never "attempted to mislead the medical community about the effectiveness" of the drug for certain uses.

"We believe the review suffers from significant bias, insufficient data, poor methodology, and cannot pass the threshold of credible scientific research," Pfizer said in a statement.

The report, by researchers at the University of California at San Francisco and the Johns Hopkins Bloomberg School of Public Health, comes two months after Pfizer was fined a record $2.3 billion — including an unprecedented $1.2 billion criminal fine — for illegally marketing other blockbuster drugs.

The report appears in Thursday's New England Journal of Medicine.

Dr. Sidney Wolfe, head of health research at consumer group Public Citizen, called it the first comprehensive look "at studies in which a company and people working for it so maliciously manipulated the data to make a drug look more effective than it actually was."

"In every instance, the published article made the drug look better than it would have," said Wolfe, a member of the Food and Drug Administration's drug safety advisory committee. "This results in harm."

Neurontin was approved by the FDA a decade ago for treating seizures and later for pain caused by shingles — but not for other conditions. Its potential side effects include suicidal tendencies and depression.

While doctors can prescribe drugs for unapproved, or off-label uses, drug companies are legally barred from promoting their products for such uses. Drugmakers often test drugs for additional conditions and publicize the results. But they don't always seek approval for those new uses, particularly if the new findings aren't convincing.