Cyclophosphamide Cyclophosphamide is an active agent in patients with a wide variety of malignancies. It is used frequently in the therapy of lymphoid malignancies and has potent immunosuppressive activity. It is frequently used as a cytotoxic and immunosuppressive agent in patients undergoing marrow transplants and as a treatment for patients with autoimmune diseases. It is an alkylating agent that requires hepatic metabolism to the active metabolites, phosphoramide mustard and acrolein. These active metabolites react with nucleophilic groups. It is available as an oral or intravenous preparation. Bioavailability is 90% when given orally. The half-life of the parent compound is 5.3 hours in adults, and the half-life of the major metabolite phosphoramide mustard is 8.5 hours. Liver or renal dysfunction will lead to prolonged serum half-life. CY is administered intravenously at a dosage of 50 mg/kg on each of two successive days (use adjusted ideal body weight if patient's actual body weight is greater than 100% ideal body weight). The major dose limiting side effect at high doses is cardiac necrosis. Hemorrhagic cystitis can occur and is mediated by the acrolein metabolite. This can be prevented by co-administration of MESNA or bladder irrigation. Other notable side effects include nausea, vomiting, alopecia, myelosuppression and SIADH. Refer to institutional manuals for more information about administration, toxicity and complications.