The interaction of ibuprofen and diclofenac with aspirin in healthy volunteers.
OBJECTIVE
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).


METHODS
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.


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
As alternatives are easily available, NSAIDs such as diclofenac should be preferred to ibuprofen for combined use with aspirin.
Schuijt
M P
MP
Clinical Chemistry, Canisius Wilhemina Hospital, Nijmegen 6532 SZ, The Netherlands.
Huntjens-Fleuren
H W H A
HW
de Metz
M
M
Vollaard
E J
EJ
D000328:Adult; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000097:blood* / Q000493:pharmacokinetics; D001241:Aspirin / Q000037:antagonists & inhibitors / Q000097:blood* / Q000493:pharmacokinetics; D018592:Cross-Over Studies; D003692:Delayed-Action Preparations; D004008:Diclofenac / Q000097:blood / Q000493:pharmacokinetics; D004347:Drug Interactions / Q000502:physiology; D005260:Female; D006801:Humans; D007052:Ibuprofen / Q000097:blood* / Q000493:pharmacokinetics; D008297:Male; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology; D012307:Risk Factors; D013929:Thromboxane B2 / Q000037:antagonists & inhibitors / Q000097:blood
D000894:Anti-Inflammatory Agents, Non-Steroidal; D003692:Delayed-Action Preparations; D004008:Diclofenac; D013929:Thromboxane B2; D001241:Aspirin; D007052:Ibuprofen