The drug Voltaren may be popular for treating aches and sporting strains but it could put users at serious risk of heart attack.
A study in the journal of the American Medical Association raised the alarm over the safety of the active ingredient dicolfenac.
Researchers surveyed the results for 1.5 million people using the anti-inflammatory and found it can increase the relative risk of heart attack and stroke by up to 40%.
"We've looked at the effects of causing heart failure, we've also looked at the propensity of dicolfenac to damage liver, and now we're looking at the propensity to cause heart attacks. So from that simple list you realise that they have a lot of side effects," says Newcastle University spokesperson David Henry.
The researchers suggest those already at risk of heart attack should consider alternative treatments.
