One of the most commonly used painkillers in Britain may put patients at an increased risk of heart attack, doctors warn today.

Ibuprofen, an anti-inflammatory drug found in millions of medicine cabinets, increased the risk by almost a quarter, according to a study. Researchers advised patients using the drug not to stop taking it, but called for further investigation of their findings.

The latest results add to the cloud of suspicion that has gathered in the past nine months over Non-Steroidal Anti-Inflammatory drugs (NSAIDs), of which ibuprofen is the most widely used.

The drug is sold over the counter without a prescription, and its best known brand is Nurofen. It is an alternative to paracetamol and aspirin used for aches and pains caused by inflammation, especially of the joints. However, the researchers point out that the absolute increase in risk is small, translating to one extra patient suffering a heart attack for every 1,005 taking the drug.

In the biggest study of its kind, researchers from the University of Nottingham surveyed 9,218 patients across Britain, aged from 25 to 100, who had a heart attack for the first time between 2000 and 2004.

They found that those prescribed NSAIDs in the three months before their heart attack were at higher risk than those who did not take the drugs. For ibuprofen the risk increased by 24 per cent and for the more powerful painkiller, diclofenac, the risk increased by 55 per cent. Diclofenac, whose brand name is Voltarol, is only available on prescription.

The researchers compared the risks with those associated with the newer generation of NSAID painkillers called Cox-2 inhibitors, which have been subject to intense scrutiny since evidence emerged in September last year that they could increase the risk of heart attack.

The bestselling Cox-2 inhibitor, Vioxx, (the chemical name is rofecoxib) which was used by 80 million patients across the world, was withdrawn that month. Evidence published in January this year suggested that it may have caused 140,000 heart attacks in American patients, of whom 44 per cent died.

In the new study, published in the British Medical Journal, the Nottingham University researchers found a 32 per cent increased risk of heart attack for patients taking Vioxx. This translated to one extra heart attack for every 695 patients treated.

The study was carried out before Vioxx was withdrawn and the authors say the findings are all the more important as many patients who were previously taking Vioxx will have switched to other drugs, including ibuprofen, without realising that these, too, carried their own risks.

"Given the high prevalence of the use of these drugs in elderly people and the increased risk of myocardial infarction [heart attack] with age, the relatively large number of patients ... could have considerable implications for public health," say the researchers, who are led by Julia Hippisley-Cox, professor of epidemiology at Nottingham University.

An editorial in the BMJ warns that the risks identified in the study may turn out not to be real because of the way patients were selected and urges caution in interpreting the findings. But it says assessment of the safety of drugs is being severely hampered by the routine concealment of crucial data by the US Food and Drug Administration.

By law, the FDA is required to make available its reports on all drugs that are approved, but it frequently deletes pages considered commercially sensitive.

In the case of a report on the Cox-2 inhibitor valdecoxib, 28 pages were deleted because they contained "trade secret and/or confidential information that is not disclosable".

The BMJ says: "Surely the protection of the public's health justifies full access to the safety data submitted by industry to the FDA and other drug licensing authorities, and mandates transparent reporting on harms, in accordance with international guidelines."

Brand names

Common brands of ibuprofen (or which contain ibuprofen)

* Nurofen

* Advil

* Motrin

* Cuprofen

* Lemsip Powercaps

* Pacifene

* Proflex