What is the action of ibuprofen?

• A. Inhibits COX-1 and COX-2
• B. Inhibits COX-2
• C. Blocks opioid receptors
• D. Inhibits COX-1

Answer: (A)

Ibuprofen works by reversibly inhibiting the enzymes COX-1 and COX-2. These cyclooxygenase enzymes convert arachidonic acid into prostaglandins, which drive inflammation, pain, and fever. By blocking both COX-1 and COX-2, ibuprofen lowers prostaglandin production across tissues, producing its analgesic, anti-inflammatory, and antipyretic effects. Because it’s non-selective, it can also reduce protective prostaglandins in the stomach and affect kidney function, which explains some GI and renal risks.

This isn’t a COX-2–selective action (that would describe drugs like celecoxib), nor does it involve blocking opioid receptors (that’s how opioid analgesics work), nor does ibuprofen inhibit only COX-1.