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 B(2) 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 B(2) 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.