Cardioprotective effects of aspirin compromised by other NSAIDsBMJ 2003; 327 doi: https://doi.org/10.1136/bmj.327.7414.520 (Published 04 September 2003) Cite this as: BMJ 2003;327:520
People who take other painkillers containing non-steroidal anti-inflammatory drugs (NSAIDs) along with aspirin could be losing the cardioprotective benefits of the aspirin, new research has suggested.
The NSAIDs, which work by interfering with the two enzymes COX 1 and COX 2, seem to compete against aspirin when the two types of drug are taken together, said Dr Tobias Kurth, lead author of the study, which was published online in advance of the print version of Circulation (http://circ.ahajournals.org).
The research supports earlier studies showing that ibuprofen can interfere with aspirin's effects. Aspirin and NSAIDs both bind to the same place on the COX 1 enzyme, but the NSAIDs bind first, thereby inhibiting the aspirin. This might explain the potential for a competitive interaction between the two, said Dr Kurth, a professor at the Harvard Medical School and the Brigham and Women's Hospital, Boston, Massachusetts. But taking other NSAIDs intermittently or occasionally did not seem to compromise the effectiveness of aspirin, he added.
The research team studied the records of 22 071 male doctors who had been taking part in the physicians' health study. They compared men who took aspirin alone with those who took other anti-inflammatory drugs for conditions such as arthritis and headache and monitored them for five years.
Aspirin reduced the risk of a first heart attack by 44% (P<0.0001). But there was no such reduction in risk among those who took aspirin as well as anti-inflammatory drugs regularly, defined as at least 60 days a year.
Among the men taking aspirin, the adjusted relative risk of having a heart attack was 1.21 (95% confidence interval 0.78 to 1.87) for additionally using NSAIDs for up to 59 days a year and 2.86 (1.25 to 6.56) for 60 or more days a year, compared with not taking additional NSAIDs. Further adjustment for known risk factors for heart attacks did not weaken the findings.
The researchers did not document which anti-inflammatory drugs the patients took. But Dr Kurth said that after the study was completed, it came to light that ibuprofen, sold under various brand names, was by far the most commonly used drug. Nor did the authors gather information on the doses of NSAIDs used, so the results describe average effects for all NSAIDs. Paracetamol (acetaminophen) would not be expected to interfere with aspirin's qualities, Dr Kurth said.