What is the mechanism of action of ophthalmic NSAIDs like ketorolac?

• A. Inhibit acetylcholinesterase
• B. Inhibit cyclooxygenase, reducing prostaglandin synthesis and inflammation/pain
• C. Block dopamine receptors
• D. Inhibit bacterial protein synthesis

Answer: (B)

Ophthalmic NSAIDs act by blocking the cyclooxygenase enzymes (COX-1 and COX-2) in ocular tissues, which stops the conversion of arachidonic acid into prostaglandins. Prostaglandins are key mediators of inflammation and pain in the eye, promoting redness, swelling, and sensitization of nerve endings after injury or surgery. By reducing prostaglandin synthesis, drugs like ketorolac lessen inflammatory swelling and the pain signals reaching sensory nerves in the eye. This mechanism is distinct from other drug actions—acetylcholinesterase inhibition affects acetylcholine levels, dopamine receptor blockade underlies antipsychotics, and inhibition of bacterial protein synthesis is the domain of antibiotics. Therefore, inhibiting COX to decrease prostaglandin production best explains the action of ophthalmic NSAIDs in reducing ocular inflammation and pain.