Yet a "substantial number" of patients continue to be prescribed high doses of the drug, according to researchers at Vanderbilt University Medical Center.
The researchers counted the number of prescriptions for non-steroidal anti-inflammatory drugs (NSAIDs), including ibuprofen, naproxen, Celebrex and Vioxx, given to participants over age 49 in Tennessee's Medicaid program, called TennCare.
Of 40,000 participants who had prescriptions for any NSAID as of July 1, 2001, nearly 10,000 were taking Vioxx, and more than 1,000 of them were "high-dose" Vioxx users, with 30-day supplies of 50-milligram pills. Half that amount -- 25 milligrams a day -- is the recommended dose for long-term use.
The 50-milligram dose has not been shown to be more effective than lower doses of the drug in relieving chronic pain, and it has been linked to an increased risk of heart attacks. "Such use should be discouraged," the researchers concluded in the June issue of the journal Pharmacoepidemiology and Drug Safety.
Vioxx (the brand name for rofecoxib) and Celebrex (celecoxib) are selective COX-2 inhibitors. They relieve inflammation by blocking the cyclooxygenase-2 enzyme, but they don't inhibit the related COX-1 enzyme, which protects the stomach lining. Therefore they don't irritate the stomach as much as NSAIDs that block both enzymes.
"They cause fewer ulcers," explained the study's lead author, Marie R. Griffin, M.D., MPH, professor of Preventive Medicine and Medicine. "That's a good thing in many ways, although there's a lot of people using them who are pretty low risk for GI (gastrointestinal) events." COX-2 inhibitors also cost $80 to $100 per month, compared to about $10 to $15 for a month's supply of generic naproxen.