Haemorrhagic cystitis occurring after high-dose cyclophosphamide is caused by a metabolite excreted in urine. The metabolite and the protective agent are:

• A Acrolein and allopurinol
• B Chloroacetaldehyde and amifostine
• C Phosphoramide mustard and leucovorin
• D Acrolein and mesna ✓

Explanation

Acrolein, a byproduct of hepatic metabolism of cyclophosphamide, is excreted in urine and directly irritates urothelium, causing haemorrhagic cystitis. Mesna is a sulfhydryl compound that binds acrolein in the bladder and detoxifies it, and is given with high-dose regimens along with vigorous hydration. Phosphoramide mustard is the alkylating antitumour metabolite, not the urotoxin. Allopurinol prevents urate nephropathy in tumour lysis, not cystitis.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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