Doctors in the UK are being warned that commonly used painkillers such as ibuprofen can increase the risk of heart attacks if taken over long periods.
The Commission on Human Medicines (CHM) has warned doctors that high doses of a class of painkillers known as non-steroidal anti-inflammatory drugs (NSAIDs), routinely taken for arthritis and back pain, "may be associated with a small risk of heart attack or stroke when used for long-term treatment.
The CHM says doctors should prescribe "the lowest effective dose for the shortest time necessary", and are requesting that manufacturers update their information on the side-effects to include "vascular events" i.e. heart attacks and strokes, as potential risks.
This latest advice follows a European review of the safety of the drugs which looked a range of research suggesting they could double the risk of a heart attack.
The research which was published in the British Medical Journal in June, examined the results of 138 trials involving 140,000 patients and found that, for every 1,000 people taking NSAIDs, three a year would suffer a related heart attack.
When all vascular events were taken together, the risks increased by 40% - twice the normal level.
However a review by the European Medicines Agency, has ruled that NSAIDs are more beneficial than harmful, provided they are not given to patients with cardiovascular or gastrointestinal problems.
The Medicines and Healthcare products Regulatory Agency (MHRA) in the UK has stressed that there is no need for patients to stop taking their medicine or to switch between different brands.
As well as ibuprofen, the committee examined diclofenac, etodolac, indomethacin, ketoprofen, ketorolac, meloxicam, nabumetone, naproxen and nimesulide.
Piroxicam is still being assessed.
The CHM says all NSAIDs carry some risk but singled out diclofenac, taken by 3.5 million people last year, as carrying a small risk of stroke if the maximum daily dose of 150mg is given.
Ibuprofen, which can be bought over the counter, carries no increased risk if used at low doses of below 1,200mg a day, but may carry a small risk of heart attack or stroke if 2,400mg, the maximum daily dose, is given.
Naproxen, taken by 500,000 people, appears to carry a lower risk of stroke, and no increased risk of heart attack, although the CHM says "some increase in risk cannot be excluded on the basis of available evidence".
The new guidance will come as another blow to millions of arthritis and back pain sufferers who rely on NSAIDs.
It was just two years ago that the arthritis painkiller Vioxx, a a COX-2 inhibitor, was withdrawn from the market after researchers found it increased the risk of heart attacks or strokes, leaving arthritis sufferers reliant on NSAIDs.
Experts say they expect many arthritis sufferers to continue to use the drugs as they are essential to those who are in a lot of pain.
Doctors and campaigners said the benefits of taking the drugs still far outweighed the risks, and that patients should not ditch their medication without speaking to their GP.
The MHRA says the warnings apply only to high doses of the drugs and the ibuprofen bought at a chemist is in a dose of about 400mg per tablet.
A high dose would be more than 2,400mg.