The new research will concern many patients who may have switched to ibuprofen and other NSAIDs after concern was raised about Cox-2 inhibitors. Millions of people around the world use ibuprofen, which is available as an over-the-counter medicine and is also used to treat minor pains, such as headaches.

But medical experts say the research on non-steroidal antiinflammatory drugs (NSAIDs), regularly used daily by arthritis patients, should be treated with caution.

Dr. Hamish Meldrum, chairman of the British Medical Association's GPs committee, said: "Patients should be reassured that although this study raises some questions, there is no need to panic. And patients should not suddenly stop taking their medicines.

"These drugs have a long and proven safety record and have been the subject of many trials which have not shown any increased risk of heart attacks.

"If patients are really concerned, they should make an appointment to discuss their treatment with their doctor the next time their medicines are due for renewal."

Low Actual Risk

Today's study from researchers at Nottingham University examined a range of painkillers and indicated that they all increased heart-attack risk when taken in the three months before the attack: Vioxx by 24 percent, Celebrex by 31 percent and ibuprofen by 24 percent. For diclofenac, it rose by over a half to 55 percent.

But this translates into a low actual risk with one extra patient for every 521 patients taking diclofenac likely to suffer a first-time heart attack. In the case of ibuprofen, one patient for every 1,005 was at risk.

In what was said to be the biggest study of its kind to date, the researchers identified 9,218 patients in England, Scotland and Wales who had suffered a heart attack for the first time during a four-year period.

They concluded that for those patients taking NSAIDs in the three months before their heart attack, the risk was greater than for those who had not taken the drugs for three years. Last year, the arthritis drug Vioxx -- part of a group known as Cox-2 inhibitors -- was withdrawn on safety grounds, with researchers suggesting it may have killed many thousands of patients.

'Excellent Safety Record'

The new research will concern many patients who may have switched to ibuprofen and other NSAIDs after concern was raised about Cox-2 inhibitors.

Millions of people around the world use ibuprofen, which is available as an over-the-counter medicine and is also used to treat minor pains, such as headaches.

It is thought that more than a million patients with arthritis have also been prescribed Cox-2 inhibitors in the UK.

The UK's Medicines and Healthcare products Regulatory Agency (MHRA) said NSAIDs were important medicines in the treatment of arthritic and other painful conditions.

The agency said it was taking part in a European-wide review of the safety of traditional NSAIDs and would be examining the new study in the context of other evidence. It added: "Ibuprofen has an excellent safety record."