Cyclophosphamide
1 medicine
Cyclophosphamide is a chemotherapy and immune-suppressing alkylating agent used for cancers and severe autoimmune disease. Its toxic byproduct can inflame the bladder, so high fluid intake or a protective drug is required.
Key facts
- Cyclophosphamide is an alkylating agent that damages the DNA of rapidly dividing cells. It treats certain cancers and calms an over-active immune system in severe autoimmune disease.
- It's given as tablets or an infusion, in cycles spaced days to weeks apart depending on the condition being treated.
- A toxic breakdown product, acrolein, can irritate and bleed the bladder lining (hemorrhagic cystitis). Drinking plenty of fluids and emptying your bladder often is essential, and higher intravenous doses are given alongside a protective medicine called mesna.
- Seek urgent care for blood in your urine, fever with chills, or unusual bruising or bleeding.
What cyclophosphamide treats
Cyclophosphamide treats cancers including non-Hodgkin and Hodgkin lymphoma, multiple myeloma, leukaemia, breast cancer, ovarian cancer, and neuroblastoma, usually as part of a combination regimen. At lower doses it is also used to control severe autoimmune and inflammatory disease that has not responded to other treatment, including lupus nephritis, ANCA-associated vasculitis, and severe nephrotic syndrome.
How cyclophosphamide works
Your liver converts cyclophosphamide into an active form that attaches to DNA inside cells and cross-links the two strands, so the cell cannot copy its DNA or divide. Cells that divide quickly, cancer cells and the immune cells driving autoimmune disease, are hit hardest, while the drug's byproducts also pass through the kidneys and bladder, where they can cause irritation.
Before you take it
- Cyclophosphamide harms a developing baby and is not used in pregnancy; discuss contraception before starting and while on treatment.
- It can cause permanent infertility in both men and women, more likely with higher cumulative doses; ask about fertility preservation before you begin if this matters to you.
- Tell your care team about any recent vaccines. Live vaccines (such as MMR, yellow fever, or oral polio) should be avoided while your immune system is suppressed.
- Existing kidney, liver, or bone marrow problems raise the risk of side effects and may change your dose.
Side effects
Common effects include nausea, vomiting, loss of appetite, fatigue, and hair loss, which usually grows back after treatment ends. Blood counts fall in the two weeks after each dose, raising infection risk.
Stop and seek urgent medical care for:
- Blood in your urine or pain on passing urine.
- Fever, chills, or other signs of infection.
- Unusual bruising, bleeding, or tiny red spots on the skin.
- A severe allergic reaction: rash, swelling, or difficulty breathing.
Safety essentials
- Hemorrhagic cystitis, bladder irritation and bleeding from a toxic breakdown product, is cyclophosphamide's defining risk. Drink the fluid volume your team recommends, urinate frequently, and take mesna if it's prescribed alongside your dose.
- Low blood counts increase infection and bleeding risk for one to two weeks after each dose; your team will check blood counts regularly and may delay the next cycle if they haven't recovered.
- Cyclophosphamide is teratogenic and can cause permanent infertility; effective contraception and a fertility discussion before treatment are essential.
This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.