A newer arthritis drug leads slightly fewer stomach side-effects than older drugs, according to a new study.

People with arthritis often take non-steroidal anti-inflammatories or NSAIDS over a long term. A newer class of NSAIDS called COX-2 inhibitors cause fewer gastrointestinal side-effects such as ulcers and stomach bleeding than other NSAIDs such as Aspirin and ibuprofen.

In the Feb. 10 issue of the medical journal The Lancet, researchers analyzed the results of three clinical trials comparing Merck & Co.'s drug etoricoxib, sold as Arcoxia, to diclofenac, sold in Canada as Voltaren. Etoricoxib is not approved for use in Canada.

"Our results indicate that the rate of clinically important upper-gastrointestinal events was lower with the COX-2 selective inhibitor etoricoxib than it was with the traditional NSAID diclofenac," said Prof. Loren Laine of the University of Southern California Keck School of Medicine in Los Angeles.

The nearly 35,000 study participants had rheumatoid arthritis or osteoarthritis.

To mirror how the drugs are prescribed in real life, participants were encourage to take a proton pump inhibitor with the drugs to protect against gastrointestinal side-effects, and those with risk factors for heart disease were urged to take low-dose Aspirin.

Overall, there were fewer ulcers in people taking the new drug and more of those people continued to take the treatment, the researchers found.

Merck employees performed the statistical analysis, which was independently confirmed by the Frontier Science Foundation.

The trial was designed to address cardiovascular side-effects, not gastrointestinal ones, Joost Drenth and Freek Verheugt of Radboud University Nijmegen, Netherlands, said in an accompanying commentary.

"Though eterocoxib reduced upper-gastrointestinal events, the effect was only small, as 259 patients need to be treated to prevent one uncomplicated gastrointestinal event," the pair wrote.

The real question is whether a COX-2 inhibitor such as etoricoxib is safer than an NSAID when a proton pump inhibitor is added, Drenth and Verheugt said.

Taking an older NSAID with a proton pump inhibitor might be cheaper and potentially less harmful to the heart, although a randomized clinical trial is needed to test the idea.

Merck pulled Vioxx, an older COX-2 inhibitor, from the market in 2004, after studies suggested it doubled the risk of heart attack and stroke in people who took it for at least 18 months.