Nociceptive pain and platelet aggregation are mediated by COX enzymes. Platelet aggregation is COX-1 dependent, whereas COX-2 is involved in inflammatory response due to tissue damage and pain. Aspirin acts by irreversible binding to COX enzyme leading to inhibition of thromboxane A2 production. Aspirin exhibits this effect for the lifetime of the platelet i.e. 7-10 days. Ibuprofen binds reversibly to the enzyme, leading to impaired platelet function only for the duration of the dosing interval.
In this article, patients received aspirin 81mg and ibuprofen 400 gm 3 times daily. Antiplatelet effects of aspirin were not reduced when ibuprofen was administered 2 hour after aspirin. When both drugs were at same time, there was reduction in antiplatelet effect of aspirin. If Ibuprofen is given first or at same time, it blocks the anti-platelet effect of aspirin due to non-specific binding to COX-1 & COX-2 enzymes. So, aspirin becomes ineffective if taken after or along with ibuprofen. In order to prevent this interaction, patients should be instructed to take ibuprofen 2 hours after the aspirin.
Posted by Prabhdeep Sidhu, PharmD Candidate 2015