Which agent is used to prevent hemorrhagic cystitis when administering cyclophosphamide?

• A. Mesna
• B. Granisetron
• C. Leucovorin
• D. Bactrim

Answer: (A)

Hemorrhagic cystitis from cyclophosphamide is caused by acrolein, a bladder-irritating metabolite. The protective approach is Mesna, a sulfhydryl-containing agent that binds acrolein in the urine to form a non-toxic complex, reducing irritation of the bladder mucosa. Because the uroprotective effect comes from this chemical interaction with acrolein, Mesna is the agent used to prevent this specific toxicity during cyclophosphamide therapy. Hydration helps flush the bladder as well.

Granisetron is an antiemetic, preventing nausea. Leucovorin is used to rescue or enhance effects in other regimens, not to prevent bladder toxicity from cyclophosphamide. Bactrim is an antibiotic, not related to uroprotection.