The common painkiller, ibuprofen, may boost the likelihood of heart problems in high risk patients who have osteoarthritis, suggests research.
Previous studies have suggested that ibuprofen interferes with the effects of aspirin.
The research team compared the cardiovascular health over one year of more than 18,000 patients aged over 50 with osteoarthritis.
The patients were taking part in the Therapeutic Arthritis Research and Gastrointestinal Event Trial (TARGET).
They were taking either high dose (400 mg a day) lumiracoxib, a type of drug known as a cyclo-oxygenase (COX-2) inhibitor, or ibuprofen (800 mg three times a day), or naproxen (500 mg twice daily), both of which are traditional non-steroidal anti-inflammatory drugs (NSAIDs).
One in 10 were considered to be at high risk of a heart attack or stroke, some of whom also took low dose aspirin (70 to 100 mg a day).
Some 623 patients were taking ibuprofen, just over half of whom (57%) were also taking low dose aspirin.
The results showed that there was no difference in the total number of heart attacks and strokes among participants at low risk of cardiovascular disease, irrespective of their drug treatment.
But this was not true of those at high risk.
High-risk patients taking aspirin and ibuprofen were around nine times as likely to have heart attacks and strokes over one year as those on lumiracoxib.
This is the first analysis of trial data to show an increased risk for ibuprofen, say the authors.
Among high risk patients not taking aspirin, the rate of heart attacks or strokes was higher for those on the COX -2 inhibitor than it was for those on naproxen, but no higher than for those on ibuprofen.
Participants taking ibuprofen also developed congestive heart failure more often than those on the COX inhibitor.
Most patients given COX-2 inhibitors and NSAIDs are elderly, and evidence to date suggests that both drug types boost the chances of heart attack and stroke.
But the authors say that their findings suggest that ibuprofen interferes with the blood thinning properties of aspirin in patients at high risk of cardiovascular disease.