Ibuprofen treatment in patients who are at increased risk of developing cardiovascular disease may limit the cardioprotective effects of aspirin therapy, according to a study in the Dec. 20 issue of the New England Journal of Medicine.
Researchers at the University of Pennsylvania School of Medicine administered 81 milligrams of aspirin two hours before administering 400 mg of ibuprofen to subjects every morning for six days, followed by a washout period of at least 14 days. They then administered the drugs in the reverse order. A second group of subjects received 1,000 mg of acetaminophen for six days and then the same drugs in the reverse order. A third group received aspirin two hours before receiving 25 mg of the cyclooxygenase-2 inhibitor rofecoxib and then received the same drugs in the reverse order.
Researchers also examined the effects of a single daily dose of enteric-coated aspirin administered two hours before the first of three 400-mg doses of ibuprofen and enteric-coated aspirin administered two hours before the first of two 75-mg doses of delayed-release diclofenac.
Results show that serum thromboxane B2 (an index of cyclooxygenase-1 activity in platelets) and platelet aggregation reached their maximum inhibition levels 24 hours after aspirin was administered on day 6 in subjects who took aspirin before a single daily dose of any other drug, as well as in subjects who took rofecoxib or acetaminophen before taking aspirin. When a single daily dose of ibuprofen was administered before aspirin or when multiple daily doses of ibuprofen were administered, however, inhibition of serum thromboxane B2 formation and platelet aggregation by aspirin was blocked.
Researchers found that concomitant administration of rofecoxib, acetaminophen or diclofenac with aspirin did not affect the pharmacodynamics of aspirin.
