Cyclophosphamide (also known as cytoxan) is an alkylator agent, meaning it has a molecular structure that binds to DNA and creates a "cross-link" that blocks replication of the DNA. It is available in an oral form but is usually given intravenously (through a small piece of tubing inserted into the patient's vein), either in a peripheral (arm) vein or a central line using a Hickman catheter, Broviac catheter, or a port-a-cath. Cyclophosfamide is used with vincristine and doxorubicin.
One of Cyclophosfamide's breakdown products in the body causes a burn to the lining of the bladder, which can lead to bleeding into the urine, called hemorrhagic cystitis. This can be prevented by aggressive hydration and receiving a second protective drug called Mesna. Mesna can be given IV or by mouth and should be taken for approximately twelve hours after a high dose of cyclophosphamide. Because cyclophosphamide kills some of the dividing cells in the bone marrow, it suppresses blood counts: low white blood cells make the immune system weak, low red blood cells (anemia) causes fatigue and short-windedness and can be treated with blood transfusions, and low platelets can increase bruising and bleeding and can be treated with transfusions.
Cyclophosphamide usually causes nausea and vomiting; medicines to prevent and treat this should be given with the dose. It also causes reversible hair loss. In high cumulative doses, it can cause sterility. Men interested in preserving fertility should consider sperm banking before therapy begins. Methods to preserve fertility in females are experimental; women with concerns should discuss this issue with their treating physician before therapy begins.