People taking the blood-thinner warfarin and a COX-2 type of painkiller are at heightened risk of upper gastrointestinal bleeding, a population-based study indicates.

The COX-2 inhibitors such as Vioxx - much in the news lately because of heart safety concerns - are intended to reduce the risk of stomach ulcers and GI bleeding compared with common nonselective nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen.

However, for patients taking warfarin, the risk of bleeding when they take COX-2 drugs (also known as coxibs) is similar to the rate seen with NSAID use, Dr. Marisa Battistella from University Health Network-Toronto General Hospital and colleagues report.

Until now, little was known about the risk of upper GI bleeding when patients take warfarin and COX-2 inhibitors together, the researchers point out in their article in the Archives of Internal Medicine.

To investigate, they linked multiple healthcare databases to identify 98,821 adults older than 66 years of age who were continuously prescribed warfarin over a period of 1 year. Of these, 361 were admitted to the hospital because of GI bleeding.

The team found that patients receiving warfarin who were admitted for GI bleeding were approximately twice as likely to have been treated with celecoxib (Celebrex) or rofecoxib (Vioxx) or an NSAID in the preceding 90 days.

While the simultaneous use of warfarin with NSAIDs is a recognized risk factor for GI bleeding, “to our knowledge our study is the first to examine the comparative safety of the COX-2 inhibitors celecoxib and rofecoxib in patients receiving warfarin,” Battistella and colleagues note.

While more study is needed, “physicians and pharmacists who care for elderly patients taking warfarin should be aware of the potential risks of concomitant therapy with NSAIDs or COX-2 inhibitors,” they warn.

Merck and Co. withdrew rofecoxib (Vioxx) from the market in September 2004 after trial data linked it to adverse cardiovascular events.

“Fortunately, many patients taking coxibs can be switched to other equally effective and evidence-based analgesic regimens,” Dr. Daniel H. Solomon, from Brigham and Women’s Hospital and Dr. Jerry Avorn from Harvard University School of Medicine, both in Boston, point out in an accompanying editorial.

SOURCE: Archives of Internal Medicine, January 24, 2005.