Azara Blog: Some painkillers allegedly increase risk of heart attack

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Date published: 2005/06/10

The BBC says:

Research has suggested all painkillers in a class of drugs, including ibuprofen and naproxen, could be linked to an increased risk of heart attack.

The drugs belong to a family known as non-steroidal anti-inflammatories.

Last year, trials raised concerns over two NSAIDs and one of them, Vioxx, was taken off the market.

The authors of the study, in the British Medical Journal, said patients should not stop taking the drugs, but called for further investigations.

Some experts questioned the validity of the study findings, saying other factors might have caused the apparent increased heart risk.

The drugs are generally used by people who have chronic pain from conditions such as arthritis.

The two drugs covered by last year's trials were COX-2 inhibitors.

They are more 'stomach friendly' alternatives to NSAIDs, which can sometimes cause ulcers and bleeding.

In the BMJ study, Professor Julia Hippisley-Cox and colleague Carol Coupland used a UK database of patients registered with a GP to identify any who had suffered a heart attack for the first time over a four-year period.

They then looked at what drugs these 9,218 patients had been taking, paying particular attention to NSAID use.

Compared with patients who had not had a heart attack, patients who had were more likely to have been taking any of four types of NSAID.

These included the two COX-2 inhibitors - Vioxx (rofecoxib)and Pfizer's Celebrex (celecoxib) - plus diclofenac and ibuprofen.

For ibuprofen, the odds increased by almost a quarter (24%), and for diclofenac it rose by over a half (55%). For celecoxib the odds increased by a fifth (21%) and for rofecoxib it rose by a third (32%).

But this translates into a low actual risk.

Therefore, one extra patient for every 521 patients taking diclofenac was likely to suffer a first-time heart attack.

For rofecoxib the figure was one patient for every 695 patients, and for ibuprofen one patient for every 1,005 patients.

Swiss medical experts from the University of Berne said in a BMJ editorial that the results should be interpreted with caution.

"The quality of the data on cardiovascular risk factors and other potential confounders was poor," they said.

The study authors admitted it was possible that other factors might have skewed their results, but they said they did take into account other heart disease risk factors such as smoking and obesity.

Trawling through patient data is a classic way to get results which confuse correlation and causation. In order to do this analysis properly you instead need to take a random set of pain sufferers, and give random subsets different pain medicines and see what the consequence is. That would prove (or not) a causation (up to stastical fluctutations). Unfortunately medical research rarely seems to be done this way because it is more expensive. Trawling databases is easy, you don't even need to get out of your chair. Of course it is obvious that all medicines carry risks. Almost any medicine will kill somebody. This does not mean nobody should take it. The real question which should always be asked is whether the risks justify the rewards. Quantifying the risks, as this study claims to do but not properly because of the non-random way it was carried out, is obviously an important step.

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