NEW YORK (Reuters) - The primary purpose of a 1999 clinical study that Merck & Co Inc said was done to test side effects of Vioxx was actually to support a marketing campaign before the now-withdrawn painkiller’s launch, according to U.S. researchers.

A pharmacist holds bottles of the prescription arthritis and pain medication VIOXX at a New York City Pharmacy after manufacturer Merc Research Laboratories announced a worldwide voluntary withdrawal of the drug September 30, 2004. REUTERS/Mike Segar

The real aim of the study, called Advantage, was to promote prescription of the new medicine when it became available -- a so-called “seeding” project -- the researchers said on Tuesday.

The research team based its conclusions on an extensive trawl of Merck internal and external documents collected by plaintiffs’ lawyers preparing for Vioxx lawsuits.

“Documentary evidence shows that Advantage is an example of marketing framed as science,” they wrote in the journal Annals of Internal Medicine.

Kevin Hill, a psychiatrist at McLean Hospital in Belmont, Massachusetts, and colleagues said the findings showed how studies masquerading as clinical science could be used to bolster marketing plans.

“Failure to disclose the primary purpose of a trial has ethical ramifications for patients, physicians and the design of clinical trials,” they said.

“Seeding trials like Advantage, in which the study medication has yet to receive (U.S. Food and Drug Administration) approval, may cause patient injury for marketing purposes.”

Merck denied that Advantage was a seeding study. It said the clinical trial had a legitimate scientific purpose in testing the gastrointestinal tolerability of Vioxx compared to the commonly used pain medicine, naproxen.

The drug maker also said the journal article contained “numerous inaccuracies” and that its conclusions were based on a limited selection of documents produced in the Vioxx litigation.

“We believe we acted appropriately with respect to the Advantage trial, and stand behind our strong beliefs in the principles of scientific integrity,” Merck said in an open letter to the editors of the medical journal.

Vioxx generated annual sales of $2.5 billion before the arthritis and chronic pain pill was withdrawn from U.S. drugstores nearly four years ago, when a Merck study showed that long-term users had twice the risk of heart attack and stroke.

Last year the company took a pretax charge of $4.85 billion for a proposed settlement with U.S. patients or their survivors who had filed Vioxx product liability lawsuits against it.