Mechanism of action of nonselective NSAIDs and typical adverse effects in dogs.

• A. Inhibit COX-1 and COX-2, reducing prostaglandin synthesis; adverse effects include gastrointestinal ulceration and potential renal impairment
• B. Inhibit COX-2 only; adverse effects include liver toxicity
• C. Block leukotriene synthesis; adverse effects include hyperglycemia
• D. Block pain receptors peripherally; adverse effects include sedation

Answer: (A)

Nonselective NSAIDs inhibit both COX-1 and COX-2 enzymes, lowering the production of prostaglandins across the board. Prostaglandins are involved in promoting pain and inflammation, but they also help protect the stomach lining and support kidney blood flow. By shutting down both COX enzymes, these drugs relieve pain and inflammation but reduce the protective prostaglandins too. That’s why the typical adverse effects in dogs are gastrointestinal upset and ulceration, along with a risk of renal impairment, especially in dehydrated or kidney-compromised animals. Other mechanisms described—selectively inhibiting COX-2, blocking leukotriene synthesis, or blocking pain receptors—don’t match how nonselective NSAIDs work or their common adverse effect profile.