ROCKVILLE, Md., Sept. 8 -- The FDA issued a caution today about the potential for attenuation of low-dose aspirin's antiplatelet effect when ibuprofen is used concomitantly for pain relief.
The agency called on doctors to inform patients about the proper timing for taking these drugs together to avoid making aspirin (81 mg/day) less effective when used for cardioprotection and stroke prevention.
It said patients who are using ibuprofen for pain relief should do so at least 30 minutes after immediate-release aspirin taken for cardioprotective or stroke-protection or at least eight hours before taking immediate-release aspirin. Ibuprofen taken this way, the FDA said, does not appear to interfere with aspirin's antiplatelet effect.
No precipitating event was cited for the aspirin-ibuprofen interaction caution, and it was not clear why the agency chose this time to issue it.
In a set of conclusions, the FDA said:
- There may be a pharmacodynamic interaction between ibuprofen and aspirin when they are dosed concomitantly. This interaction may interfere with the antiplatelet activity of the aspirin, as measured by TXB2 levels and platelet activation.
- The clinical implication of this interaction is unclear, but may be important since the cardioprotective effect of aspirin, when used for secondary prevention of myocardial infarction, could be minimized or negated.
- A negative clinical impact on aspirin's cardioprotection is unlikely from an occasional dose of ibuprofen because the effect of aspirin taken daily is long-lasting.
"Existing data using platelet function tests suggest there is a pharmacodynamic interaction between 400 mg of ibuprofen and low dose aspirin when they are dosed concomitantly," the FDA said. "The FDA is unaware of data addressing whether taking less than 400 mg of ibuprofen interferes with the antiplatelet effect of low dose aspirin. There has not been a prospective, randomized clinical trial with pre-identified cardiovascular endpoints that could provide data to clarify the clinical consequence of such concomitant dosing with ibuprofen and low dose aspirin."
The agency added:
- Other nonselective OTC NSAIDs should be viewed as having potential to interfere with the antiplatelet effect of low-dose aspirin unless proven otherwise.
- Analgesics that do not interfere with the antiplatelet effect of low dose aspirin should be considered for populations at high risk for cardiovascular events.
Acetaminophen appears to not interfere with the antiplatelet effect of low dose aspirin, said the agency.
The FDA said it was "unaware of studies that have looked at the same type of interference by ketoprofen with low dose aspirin. One study of naproxen and low-dose aspirin has suggested naproxen may interfere with aspirin's anti-platelet activity when they are co-administered. However, naproxen 500 mg administered two hours before or after the administration of aspirin 100 mg did not interfere with aspirin's antiplatelet effect. There are no data looking at doses of naproxen less than 500 mg."