Patients on Warfarin Should Avoid Cox-2 Drugs

Older patients taking the blood-thinner warfarin have an elevated risk of potentially deadly stomach bleeding if they also take common anti-inflammatory drugs for arthritis, a Canadian study suggests.

This danger isn’t limited to drugs such as ibuprofen or Naproxen. Celebrex®, Bextra®, and Vioxx®, also pose a risk, says Muhammad Mamdani, a senior author of the study by the Institute of Clinical Evaluative Sciences (ICES).

"So first and foremost, if you’re on warfarin, and you need to take one of these drugs, be careful because your risk of bleeding doubles," Mamdani, an expert in pharmacology and health research, said in a recent interview. Warfarin, taken by thousands of older Canadians to prevent heart attacks and strokes from blood clots, makes it more difficult to stop bleeding from a cut or other injury.

Early studies suggested Cox-2 inhibitors like Celebrex® were "safer on the gut than traditional NSAIDs," said Mamdani. "Our study was finding they both have the same rates of gastrointestinal bleed." The condition can be dangerous: about one in 10 patients with serious stomach bleeding die before making it to the hospital for life-saving surgery, he said.

The researchers analyzed several prescription and health-care databases in Ontario, looking at patients over age 66 that were on warfarin during a yearlong study in 2000-2001. They found that those admitted to the hospital for gastric bleeding were more likely to be taking NSAIDs or Cox-2 inhibitors along with the blood thinner.

The study is published in January’s issue of the Archives of Internal Medicine.

Mamdani said the analysis also showed that "physicians seem to be a little more lax in prescribing Cox-2 inhibitors," noting that twice as many older people on warfarin are given a Cox-2 compared with NSAIDs.

Dr. Jim Wright, a clinical pharmacologist and internist at the University of British Columbia, said the study has major implications because a lot of physicians would likely choose Cox-2’s for arthritis patients already on warfarin, believing the drugs have a lower risk than NSAIDs. Wright said that assumption is now wrong and has not been backed up by previous studies.

"I’ve been saying for a long time that these drugs are probably more harmful than beneficial compared to NSAIDs… I’ve been recommending not to use these until there’s clear evidence that they’re safer. And that hasn’t happened."

"And the evidence we have right now suggests we shouldn’t use them."

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