Merck & Co’s arthritis pill Vioxx was pulled from market shelves over health risks in 2004, after a study showed the drug increased the risk of heart attacks and strokes twice if it was taken for more than 18 months.

Now a new long-tern follow-up study appears to back previous findings, namely the drug nearly doubles the risk of heart attack and stroke compared to no treatment at all. Moreover, the risk persists for approximately a year, according to Dr. Robert Bresalier, a professor of medicine at the M.D. Anderson Cancer Center in Houston and co-author of the study. The good news is “the risk goes back toward normal after a year of follow up” he added.

For the study, Dr. Bresalier and colleagues followed people who had participated in the international APPROVe trial, which compared Vioxx to placebo over 3 years in an attempt to see whether the drug could reduce the recurrence of cancerous colon polyps. The study was stopped early in 2004 because of the increased risk for heart attacks and strokes.

Almost 2,600 people were involved in the trial. The researchers succeeded to contact 84 percent of them and found that a year after finishing Vioxx treatment, those given the pill had a 79 percent increased risk of heart attack, stroke compared with those who had received placebo. Also, their relative risk of death was 31 percent higher.

“Our data are compatible with an early increase in risk that seems to persist for about one year after three years of treatment. The cardiovascular toxicity seems to be a class effect. Indeed, studies of other selective COX-2 inhibitors reported similar findings,” the researchers concluded. Cox-2 drugs were designed to be safer replacements for NSAIDS, including aspirin and naproxen, which can cause deadly gastrointestinal bleeding.

A statement released by Doug Watson, a cardiovascular epidemiologist and senior director at Merck Research Labs says the overall findings were consistent with the original study, but the company officials believe that the research “using limited data from a prematurely terminated study needs to be interpreted very cautiously and in the context of the rest of the data from the extensive clinical development program for Vioxx.”

Last year, Merck paid 4.85 billion dollars to settle 27,000 lawsuits filed by people saying they or their family members suffered injury from Vioxx painkiller drug. As of Oct. 9, 2007, in the United States, the Company had been served or was aware that it had been named as a defendant in approximately 26,600 lawsuits, filed on or before Sept. 30, 2007, which include approximately 47,000 plaintiff groups, alleging personal injuries resulting from the use of Vioxx.

Vioxx had generated sales of $2.5 billion a year before the arthritis and chronic pain pill was withdrawn from U.S. drugstores in 2004.

The study was published online in the Oct. 14 issue of British medical journal The Lancet.