Do aspirin and ibuprofen block COX-1 and COX-2?

• A. Yes
• B. No
• C. Only COX-1
• D. Only COX-2

Answer: (A)

Both aspirin and ibuprofen are non-steroidal anti-inflammatory drugs that block the enzymes called cyclooxygenases, COX-1 and COX-2, which normally convert arachidonic acid into prostaglandins and thromboxanes. Blocking COX-1 reduces thromboxane A2 in platelets (lowering clotting) and also lowers protective gastric prostaglandins, while blocking COX-2 lowers inflammation and pain. Aspirin inhibits these enzymes irreversibly—especially COX-1 in platelets—so its effects on platelets last for the life of the platelet. Ibuprofen inhibits both enzymes reversibly, with effects that wear off as the drug is cleared. So, overall, both drugs block COX-1 and COX-2, though the duration and reversibility differ.