THOUSANDS OF Irish patients who are prescribed aspirin to prevent heart attacks and strokes have been warned that taking a common painkiller at the same time could interfere with the clot-busting effect of aspirin.
In its latest drug safety bulletin, the Irish Medicines Board (IMB) said it has told manufacturers of ibuprofen, the commonly used anti-inflammatory drug, to update its product information to advise patients who are taking the drug on a long-term basis to leave an eight-hour gap before ingesting low-dose aspirin.
Alternatively, patients are advised to wait for 30 minutes after taking low-dose aspirin before they swallow any ibuprofen.
The warning comes after research suggested that ibuprofen, which is taken by many patients with arthritis, can inhibit the anti-platelet effect of aspirin.
Low-dose aspirin is prescribed for most patients who have a history of cardiovascular disease, or who are thought to be at risk of having a heart attack or stroke, because of its ability to stop platelets clumping together to form clots in blood vessels.
The drug works by inhibiting an enzyme, cyclooxygenase-1 (COX-1).
However, ibuprofen also inhibits the working of the same enzyme, as both drugs compete for the same site on COX-1, leading to the possibility of the aspirin being “crowded out” by the anti-inflammatory drug and so unable to exert its cardioprotective effects.
While no randomised controlled trials into the problem have yet been carried out, Dr Joan Gilvarry, director of Human Medicines with the Irish Medicines Board, told The Irish Times, “there is a potential risk and to minimise this risk people should be careful about the timing of administration of both medicines”.
The IMB has asked companies that manufacture ibuprofen to update their summary of product characteristics (SPC) to include the following information: “in one study, when a single dose of ibuprofen 400mg was taken within eight hours before or within 30 minutes after immediate release aspirin (81mg), a decreased effect of aspirin on the formation of thromboxane or platelet aggregation occurred”.
However, it goes on to say that no clinically relevant effect is likely in people who use ibuprofen occasionally.
Ibuprofen is prescribed under a number of trade names including Brufen, Melfen and Provin.
It is also available over the counter as Nurofen. It is a mild to moderate painkiller used for musculoskeletal injury and dental pain.
Older people with osteoarthritis or rheumatoid arthritis are those who are most likely to take the drug on a prolonged basis; they are also the group of patients which is likely to require low-dose aspirin for cardiac prevention.
Other medicines that may affect or be affected by ibuprofen include blood pressure medication in the form of ACE inhibitors and beta blockers.
Ibuprofen, along with other non-steroidal anti-inflammatory drugs, may also precipitate bleeding in the gastrointestinal system.