A 45-year-old man with chronic low-back pain has been taking aspirin 325 mg daily for cardioprotection. He now requires NSAID therapy for acute pain. His physician prescribes ibuprofen. What is the most important drug interaction concern and the recommended timing?
- A Ibuprofen increases aspirin ototoxicity; separate doses by 4 hours
- B Aspirin reduces ibuprofen renal clearance; reduce ibuprofen dose by half
- C Ibuprofen competitively blocks aspirin access to platelet COX-1; give aspirin at least 2 hours before ibuprofen ✓
- D Both drugs increase risk of Stevens-Johnson syndrome; avoid combination entirely
Correct answer: C. Ibuprofen competitively blocks aspirin access to platelet COX-1; give aspirin at least 2 hours before ibuprofen
Explanation
Ibuprofen binds reversibly to the COX-1 channel and can block aspirin's access to its serine-530 acetylation site if taken concurrently. If ibuprofen is taken before aspirin, the antiplatelet effect is lost. Giving aspirin at least 2 hours before ibuprofen avoids this interaction. This is a well-documented clinically significant interaction. Option D overstates the dermatological risk.
Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.