Cyclophosphamide (Cytoxan)


Cyclophosphamide (Cytoxan) is a potent immunosuppressant that can decrease the immune response by blocking the production of DNA in cells. Cyclophosphamide is used for severe complications of systemic lupus erythematosus (SLE), systemic sclerosis (scleroderma), some forms of vasculitis, myopathies, such as polymyositis and dermatomyositis; and sometimes rheumatoid arthritis.

How to Take It

Cyclophosphamide is often used for three - six months to treat a condition and put it into remission.  Afterwards, a medication that may be less potent with fewer side effects is used to maintain the disease in remission. In some cases, cyclophosphamide can be used as a maintenance therapy for certain conditions.

Cyclophosphamide can be taken orally daily or can be given by injection given at the doctor's office or hospital every week to every month. The dosing of cyclophosphamide varies from person to person and depends on the disease being treated. The oral form is given 1.5 to 2.5mg/kg of body weight per day. The dose for the injectable form is either calculated based on height, weight and kidney function or it’s given as a fixed dose of 1g every 4 weeks, or 500 mg IV every two weeks for six weeks. It may take several weeks for symptoms to improve and the full effect may take several months or longer. 

Side Effects

Common side effects, which may be worse with the pill form, include nausea and vomiting. These symptoms usually can be controlled with anti-nausea medications. Hair loss can occur, but hair usually will grow back when the medication is stopped. Other common side effects include skin rashes. Cyclophosphamide can increase the risk of developing some kinds of infections, especially shingles.

Cyclophosphamide may cause reduced number of white blood cells. This can occur 8-12 days after starting treatment. Your doctor will check your blood counts around this time and make dose adjustments as needed.

Cyclophosphamide can also cause infertility in both men and women. Although women taking cyclophosphamide can stop having periods, they can still become pregnant, so an effective form of birth control to prevent pregnancy should be used while taking this medication. Taking cyclophosphamide during pregnancy is very dangerous to an unborn child.

Cyclophosphamide may result in blood in the urine or scarring of the bladder. Patients taking oral cyclophosphamide should drink plenty of fluids each day to help prevent problems. A medication called mesna may help prevent bladder problems. Cyclophosphamide also increases the risk of developing some kinds of cancer, including lymphoma, skin and bladder cancer (periodic urine tests screen for this). 

Tell Your Rheumatology Provider

Before starting, let your rheumatology provider know all medications you are taking, including over-the-counter medicines and herbal supplements. Notify your other physicians when taking this drug or have been given this in the past. There are some long-term risks to be considered even years after taking the medication.

Live vaccines should be avoided while on this medication, and caution should be taken if any household members receive live vaccines. You should discuss updating your vaccinations prior to starting this medication. Women who are pregnant or considering becoming pregnant should talk with their doctor before taking this drug. You should contact your rheumatology provider if you notice the following: blood in your urine, fevers and chills, easy bruising or bleeding, shortness of breath, and/or swelling of the feet and ankles.

Updated February 2022 by Mohammad Ursani, MD, and reviewed by the American College of Rheumatology Committee on Communications and Marketing.

This information is provided for general education only. Individuals should consult a qualified health care provider for professional medical advice, diagnosis and treatment of a medical or health condition.

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