Cyclophosphamide

Cyclophosphamide is a cytotoxic chemotherapy agent in the alkylating nitrogen mustard class. It is a prodrug that is metabolized in the liver by cytochrome P450 enzymes to active metabolites, notably phosphoramide mustard, which forms DNA cross-links and disrupts replication, leading to cell death. It is non–cell-cycle–specific and affects both dividing and resting cells. Commercially it is sold under various names, including Cytoxan.

In oncology, cyclophosphamide is used for several hematologic malignancies such as non-Hodgkin lymphoma, chronic and acute leukemias, and multiple myeloma, and it is employed in various solid-tumor regimens. It is often part of combination therapies and may be given as high-dose therapy with stem cell support in conditioning regimens for bone marrow transplantation. In autoimmunity, it is used for severe systemic lupus erythematosus, vasculitis, and nephrotic syndrome when other treatments are inadequate or contraindicated.

Administration and safety measures include oral tablets and intravenous infusions. Dosing is typically based on body surface area and regimen. High-dose regimens may require uroprotection with mesna and aggressive hydration to reduce hemorrhagic cystitis; regular monitoring of blood counts, kidney and liver function is standard. Common adverse effects include myelosuppression, nausea, vomiting, alopecia, and mucositis. Other risks include infertility, increased infection susceptibility, hemorrhagic cystitis, and a potential risk of secondary malignancies. Pregnancy is contraindicated. Drug interactions with other myelosuppressants or nephrotoxic agents require careful management.