The interaction of ibuprofen and diclofenac with aspirin in healthy volunteers

Background and purpose:  Aspirin reduces the risk of myocardial infarction and stroke by inhibiting thromboxane production in platelets. This inhibition can be competitively antagonized by some non‐steroidal anti‐inflammatory drugs (NSAIDs).

Experimental approach:  By measuring thromboxane B₂ production in healthy volunteers, we investigated whether ibuprofen (800 mg three times daily for 7 days) or diclofenac (50 mg three times daily for 7 days) taken concurrently with aspirin 80 mg (once daily for 7 days) influenced the inhibitory effect of aspirin. The effects were compared with aspirin 30 mg (once daily for 7 days), which is the lowest dose of aspirin with a proven thromboprophylactic effect.

Key results:  The median percentage inhibition of thromboxane B₂ levels by 30 mg or 80 mg aspirin was 90.3% (range 83.1–96.0%) and 98.0% (range 96.8–99.2%) respectively. The inhibition by concurrent administration of slow release diclofenac and 80 mg aspirin was 98.1% (range 97.2–98.9%), indicating no interference between aspirin and diclofenac. The inhibition decreased significantly by concurrent administration of immediate release ibuprofen and 80 mg aspirin (86.6%; range 77.6–95.1%) to a level less than 30 mg aspirin.

Conclusions and implications:  As alternatives are easily available, NSAIDs such as diclofenac should be preferred to ibuprofen for combined use with aspirin.

DOI: 10.1111/j.1476-5381.2009.00243.x

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