By Patricia Reaney Thu Jun 1, 7:02 PM ET

LONDON (Reuters) – High doses of some older painkillers as well as newer drugs known as COX-2 inhibitors raise the risk of a heart attack, scientists said on Friday.

But they said the increased risk was moderate and comparable to what is accepted with other drugs.

“COX-2 inhibitors and NSAIDs (non-steroidal anti-inflammatory drugs), particularly ibuprofen and diclofenac increase the risk of heart attacks,” said Dr Colin Baigent, an epidemiologist at the University of Oxford in England.

Baigent and researchers in Italy analyzed previous studies into the use of COX-2 inhibitors and NSAIDs in a meta-analysis which included data from 138 trials and 140,000 patients.

As expected, they found that COX-2 inhibitors were linked with a moderate increase in the risk of heart attacks. But the research also showed that high doses of some NSAIDs carried similar odds.

“We have put together all the randomized trials that have been conducted using COX-2 inhibitors and NSAIDs and come up with a synthesis of the overall evidence — everything that is available,” Baigent explained in an interview.

“It gives us a uniquely reliable result.”

The increased risk means that for every 1,000 people taking an NSAID or COX-2 inhibitor about three extra people a year would have a heart attack.

Vioxx, a COX-2 inhibitor made by Merck & Co., was pulled from the market in 2004 after research showed it doubled the risk of heart attack and stroke in people who took it for at least 18 months.

The company is facing more than 11,500 Vioxx lawsuits.

Baigent, who reported the findings in the British Medical Journal, said the drugs eased chronic pain in people who cannot manage to go about their daily lives without some relief.

Patients with pain from arthritis or other conditions are advised to take the lowest possible dose of the drug that relieves symptoms and take that dose for the shortest possible time.

“Our research backs that up. That is the sensible policy given the results,” Baigent.

NSAIDs relieve pain by blocking the action of enzymes called cyclooxygenases (COX), which control inflammatory responses. Although they are effective, the drugs can cause ulcers and dangerous stomach bleeding.

COX-2 inhibitors were designed as a safer long-term alternative to NSAIDs.

Professor Peter Weissberg of the British Heart Foundation said the research added to the growing body of evidence showing high doses of NAIDS could be dangerous.

“However, the increased risk is small and many patients with chronic debilitating pain may well feel that this small risk is worth taking to relieve their symptoms,” he said in a statement.