What preventive measure reduces bladder toxicity with cyclophosphamide?

• A. Diuresis
• B. Frequent voiding
• C. Adequate hydration and frequent voiding
• D. No hydration

Answer: (C)

The preventive measure being tested is using adequate hydration together with frequent voiding to protect the bladder. Cyclophosphamide is metabolized to acrolein, a toxic substance that can irritate and damage the bladder lining, leading to hemorrhagic cystitis if it stays in the bladder. By drinking enough fluids, you increase urine volume, which dilutes acrolein and reduces its contact time with the bladder mucosa. Encouraging frequent voiding ensures the bladder is emptied regularly, helping remove the irritant more quickly. This combined approach is more effective than just forcing fluids without ensuring bladder clearance or relying on voiding alone without sufficient hydration. Not hydrating would substantially raise the risk of bladder toxicity. (In some regimens, additional protection like mesna is used, but the hydration and frequent voiding strategy is a fundamental preventive measure.)