Pharmacology: Mesna is sulfhydryl containing compound which is excreted in the urine. Co-administration with Oxazaphosphorine alkylating agents such as Ifosfamide and Cyclophosphamide significantly reduces their urotoxic effects by reacting with the causal metabolites, including acrolein, in the urinary system. No reduction in the anti-tumour activity of these Oxazaphosphorine compounds has been detected.