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The popular pain reliever ibuprofen blocks the heart-protecting effects of aspirin, according to a new study (NEJM 2001 (Dec 20): 345 (25): 1809-1817). The results, if confirmed, would have major implications for millions of people who take a small dose of aspirin every day for their hearts, but who also take ibuprofen, widely known in North America under the brand names Advil and Motrin, to cope with conditions such as arthritis.
In other research published in the same issue of the New England Journal, doctors in Sweden and Nashville found that aspirin and acetaminophen seemed to increase the risk of long-term kidney failure.
“It would not do you a lot of good to take one medication only to have another wipe out its effects,” said Dr. Muredach Reilly, a University of Pennsylvania cardiologist who took part in the 30-patient study reported in Thursday’s New England Journal of Medicine.
Many heart patients regularly take aspirin because it thins the blood and prevents the clots that cause heart attacks.
In the study, when patients took a single dose of ibuprofen beforehand, aspirin lost 98 percent of its blood-thinning power. When aspirin was taken first, three daily doses of ibuprofen sapped aspirin of 90 percent of its benefit.
The researchers believe that ibuprofen clogs a channel inside a clotting enzyme known as cyclooxygenase-1. Aspirin gets stuck at the bottleneckand cannot reach its own active site inside the enzyme.
The study found show no conflict between aspirin and three other arthritis drugs: diclofenac (best known as Voltaren), acetaminophen (Tylenol) and refocoxib (Vioxx). But the researchers suggested that other drugs with structures like ibuprofen, such as indomethacin, will similarly block aspirin.
Ibuprofen belongs to a widely used class of pain relievers known as nonsteroidal anti-inflammatory drugs.
“This isn’t an indictment of all nonsteroidals, but it does give one pause,” said Dr. Leslie Crofford, an arthritis specialist at the University of Michigan. She wrote an accompanying editorial.
She said researchers should now study humans to verify if these laboratory findings translate into a real danger of heart attacks.
The study was funded partly by the National Institutes of Health and aspirin maker Bayer.
Fran Sullivan, a spokesman for Advil maker Whitehall-Robins Healthcare of Madison, N.J., said if the study is right, “it’s more a matter of timing.” He suggested that regular aspirin be taken two hours before ibuprofen. He said enteric-coated aspirin, which is released more slowly into the blood, could be taken at bedtime without a conflict.
On Thursday, the journal also published a separate study that showed a greater risk of chronic kidney failure in patients who regularly take either aspirin or acetaminophen (NEJM 2001 (Dec 20): 345 (25): 1801-1808). Earlier research suggested similar side effects.
Using medical records and interviews from Swedes, both with kidney failure and without, Dr. Michael Fored of the Karolinska Institute in Stockholm found the 926 people with kidney failure were 2.5 times more likely to have been regular users of aspirin and acetaminophen than the 998 without kidney problems.
Leslie Crofford of the University of Michigan in Ann Arbor, in an accompanying editorial, noted the problem wasn’t seen in people taking a low dose of aspirin to prevent a heart attack. And people without any preexisting kidney disease faced a low risk of kidney failure, even if they were taking the aspirin and the nonsteroidal anti-inflammatory drugs, Crofford said.
But, “In patients with progressive renal (kidney) disease,” Crofford said, “all these drugs, with the exception of low-dose aspirin, are best avoided if possible.”