To prevent urothelial toxicity from chemotherapy, which drug is most likely prescribed?

• A. Amifostine
• B. Mesna
• C. Dexrazoxane
• D. Leucovorin

Answer: (B)

Mesna is used to prevent bladder (urothelial) toxicity from certain chemotherapy regimens. Its job is to neutralize acrolein, the toxic metabolite produced when agents like ifosfamide (and sometimes cyclophosphamide) are broken down in the body. Mesna contains sulfhydryl groups that bind acrolein in the urine, forming non-toxic adducts that are then excreted, which markedly reduces the risk of hemorrhagic cystitis.

The other agents protect against different toxicities or have different roles: amifostine mainly protects against renal toxicity from cisplatin; dexrazoxane protects the heart from doxorubicin and can be used for extravasation; leucovorin rescues or enhances effects in methotrexate or 5-FU therapy. None of these specifically prevent urothelial toxicity from ifosfamide/cyclophosphamide like Mesna does.