Why are ketones present in urinalysis results when patients are receiving ifosfamide or cyclophosphamide?

These drugs are alkylating agents that increase the risk of hemorrhagic cystitis. Acrolein, the metabolized byproduct of these agents, is excreted by the kidneys into the urine. If allowed to remain in contact with the bladder mucosa, acrolein can cause irritation, inflammation, and bleeding. A urinalysis is performed to look for blood in the urine and to assess hydration status. Mesna (Mesnex) is a uroprotective agent that helps to prevent hemorrhagic cystitis. When given IV, it can be mixed with ifosfamide or cyclophosphamide and given after as IVPB. If given PO, the dose is higher and the drug is foul-tasting. Mesna is a free-sulfhydryl compound. It is these compounds that react to the ketone pad on the urine dipstick and cause the false-positive reading. Careful attention to the urinalysis is needed to check for the presence of blood and the specific gravity reading to assess the patient’s hydration status. — Karen MacDonald, RN, BSN, CPON