This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
All the following drugs are reversible inhibitors of COX EXCEPT- 
Select and explain. 
A. Diclofenac, B. Ibuprofen, C. Aspirin, D. Indomethacin
C: Aspirin
Answer: C: Aspirin 
Explanation: Ans. is 'c' i.e., Aspirin o Aspirin inhibits COX irreversibly by acetylating one of its serine residues, return of COX activity depends on synthesis of fresh enzyme. Other NSAIDs are competitive and reversible inhibitors of COX, return of activity depends on their dissociation from the enzyme which in turn is governed by the pharmacokinetic characteristics of the compound.