There is a drug-drug interaction between ibuprofen and aspirin, with ibuprofen affecting aspirin’s ability to inhibit platelet clumping or aggregation that can lead to fatal blood clots, investigators at the University of Buffalo, New York and Dent Neurologic Institute in Amherst, New York, have found.

Dr. Francis Gengo and colleagues note that they compared the extent and duration of platelet clumping with aspirin 325 mg alone, with ibuprofen alone and with aspirin 325 mg given two hours after ibuprofen 400 mg in 12 healthy subjects.

The subjects took each medication or medication combination for five days and the investigators assessed platelet clumping in whole blood samples using standard tests.

According to the results, presented this week at the 35th annual meeting of the American College of Clinical Pharmacology, duration of inhibition of platelet aggregation with aspirin alone was 72 to 96 hours.

This was significantly longer than the inhibition of only 4 to 6 hours with aspirin followed by ibuprofen, and with ibuprofen alone.

Thus, the presence of ibuprofen prevents the irreversible inhibition of platelet clumping produced by aspirin needed for secondary prevention of stroke, Gengo said.