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Cytoxan (cyclophosphamide)

What is Cytoxan?

Cytoxan is a brand name of the medication Cyclophosphamide. Cytoxan is used in chemotherapy and is used to suppress the immune system. It is used to treat a number of different cancers including leukemia, lymphoma, Hodgkin’s disease, small cell lung cancer, multiple myeloma, neuroblastoma, retinoblastoma, and cancers of the soft tissues.

It can also be given for severe rheumatoid arthritis or connective tissue diseases. This usually only occurs in very severe cases with evidence of effects in the whole body.

Cytoxan can be given as a tablet or as an injection.

How does it work?

Cytoxan belongs to a group of medicines called antineoplastics, meaning that they work against cancers. It is in a sub-group of this family of medicines known as alkylating agents. Once the medication is administered, the body converts the drug to active components acrolein and phosphoramide. These active components impact the genetic material, the DNA of the cancer cells which prevents them from replicating and multiplying. Unfortunately, Cytoxan is not able to tell normal cells form cancer cells. This means that normal, healthy cells are also affected. This can cause serious side effects for anyone using this medication. It also causes the immune system to be suppressed which can make you more prone to infections, including those to which you would not normally be susceptible.

How to use

Cytoxan can be taken as an injection or as a tablet. The injection comes in 500mg, 1g and 2g vials. This is usually dissolved a small amount of saline or glucose and given as an infusion. This is usually administered once or twice per week.

The tablets come as 25mg or 50mg and are taken orally each day.


The dose will vary depending on the condition it is prescribed to treat as well as other medicines that you are taking. It also depends on your body weight and the method of administration, as tablets or injection. Your doctor will advise on the best schedule of treatment for you.

As an injection, Cytoxan is administered up to twice a week in a clinical setting. It must be given and supervised by a medical professional in a sterile manner. It is then applied intravenously. It is possible that larger doses may be administered every three to four weeks during the course of treatment.

Tablets are given as a daily dose, much smaller than the injected form as it is taken on a daily basis. As with the injections, larger doses may be given every three to four weeks.  The tablets are best taken first thing in the morning along with food. Your doctor will advise as to your dosing schedule.

Doses are usually smaller when used for severe rheumatoid arthritis or connective tissue disease. If using injections, they are usually administered every 2 weeks. If in doubt about the form and dose of your medication, consult your doctor. Tablets are taken orally on a daily basis but usually at a lower dose than would be used for cancer.

Side Effects

Some people may experience an allergic reaction to Cytoxan. Stop taking medication immediately and seek medical attention if you experience signs of a severe allergic reaction. Typically, this would manifest as hives, difficulty breathing and/or swelling of the face or throat.

Some people may experience skin reactions when using Cytoxan. Stop taking medication immediately and seek medical attention if you experience signs of a skin reaction. This would include blistering, peeling of skin, or a rash that covers a large area, spreads quickly or is associated with a fever. Cytoxan can be absorbed through the skin. It is important to wash your hands if you have come in to contact with broken tablets or capsules. You should try to avoid inhaling any powder produced by broken tablets or capsules.

Some people may experience seizures when taking Cytoxan. If this occurs, stop taking the medication and seek immediate help from a healthcare professional.

At least 1% of people experience some of the following side effects:

  • Fatigue
  • Nausea
  • Diarrhea
  • Headache
  • Loss of appetite
  • Vomiting
  • Temporary hair loss
  • Blood and bone marrow disorders

Rare but serious side effects can occur. If you experience any of the following side effects, contact your doctor as soon as possible:

  • Blood in your urine
  • Burning or pain when urinating
  • Confusion
  • Dizziness
  • Fever or chills accompanied by cough or hoarseness
  • Strange sensations in arms or legs, such as tingling, prickling or numbness
  • Redness, swelling or pain at the site of injection
  • Anemia – signs to look out for include dizziness, pale skin, unusual tiredness or weakness, shortness of brearth
  • Heart failure – signs to look out for include shortness of breath, fatigue, swelling of feet, ankles or legs
  • Infection – signs to look out for include fever or chills, severe diarrhea, shortness of breath, prolonged dizziness, headache, stiffness, weight loss, listlessness
  • Infertility in both men and women
  • Kidney problems – signs to look out for include increased urination at night, decreased urine production, blood in urine, change in color of urine
  • Liver problems – signs to look out for include nausea, vomiting, diarrhea, loss of appetite, weight loss, yellowing of the skin or eyes, dark urine and pale stools
  • Inflammation of the lungs – signs to look out for include darkening of lips and fingernails, persistent cough, burning sensation in the chest
  • Mouth and lip sores
  • Low blood pressure – symptoms to look out for include fainting, dizziness, light-headedness, blurred vision, increased thirst, nausea
  • Low platelets – any cuts or grazes will bleed for longer, bruises occur frequently after minimal trauma
  • Syndrome of inappropriate antidiuretic hormone secretion – SIADH – symptoms to look out for include nausea and vomiting, cramps, tremors, depressed mood, memory impairment, irritability, personality changes, confusion, hallucinations, and seizures
  • Vein inflammation from injections

As with many medicines used in cancer treatment, it is possible that use of Cytoxan can lead to the development of other secondary cancers.

Decision to take Cytoxan should be made in conjunction with your doctor. All benefits and risks, including side effects, should be discussed and a fully informed decision should be made.

You may experience side effects other than those listed above. Always check with your doctor if you are concerned.

Warnings & Precautions

It is important to let all of your healthcare providers know all of the medication that you are taking, all of the conditions that you have been diagnosed with and any allergies that you may have. Remember to include any over the encounter medications, vitamins, supplements, herbal medicines, and recreational drugs.

Cytoxan should be avoided in those with acute porphyrias or diabetes mellitus. Also avoid in those with hemorrhagic cystitis and in those receiving mediastinal irradiation.

If there is impairment in liver or kidney function, doses may need to be reduced. This should be discussed with your doctor. If there is severe liver or kidney dysfunction it may not be possible to safely take this medicine. Cytoxan is metabolised by the liver and can lead to damage of the bladder if urine is kept there for a prolonged period. Drinking lots of fluids and frequent urination can help to reduce this risk.  It is recommended that you take the advice of your doctor.


Medications known to interact with Cytoxan:

  • Adalimumab
  • Alemtuzumab
  • Allopurinol
  • Amiodarone
  • Amphotericin B
  • Azathioprine
  • Bacillus Calmette-Guerin (BCG)
  • Belimumab
  • Carbamazepine
  • Ciprofloxacin
  • Clozapine
  • Colchicine
  • Cyclosporin
  • Dabrafenib
  • Deferiprone
  • Denosumab
  • Digoxin
  • Echinacea
  • Efavirenz
  • Etanercept
  • Filgrastim
  • Fingolimod
  • Grapefruit juice
  • HIV protease inhibitors
  • Indomethacin
  • Leflunomide
  • Lumacaftor
  • Mifepristone
  • Natalizumab
  • Nevirapine
  • Other cancer medications
  • Pentostatin
  • Phenobarbital
  • Phenytoin
  • Pimecrolimus
  • Rifampin
  • Roflumilast
  • Tacrolimus
  • Thiazide diuretics
  • Tofacitinib
  • Vaccines
  • Warfarin

If you are on any of the medications mentioned above consult with your doctor or your pharmacist. It may be necessary to stop taking one of the medications; change one of the medications to an alternative; change how or when you take one or both medications; or your healthcare professional may decide it is best to leave all medications as they are.

The list above is not exhaustive and may not contain all medications known to interact with Cytoxan. It is important that you inform your doctor of all medications, herbal medicines, supplements, over the counter medication and recreational drugs that you are taking.


Cytoxan should not be used if there is a known allergy to cyclophosphamide.

Do not use in those who are pregnant or breastfeeding.

Do not use if you have severe bladder problems.

Do not use if you have severe liver or kidney problems.

Do not use if you have low platelets or a low white cell count.

Do not use if you have an active infection.

Inform your doctor if any of the contraindications mentioned above apply to you.

Frequently Asked Questions

Cytoxan is a brand name for the drug cyclophosphamide. It is used to treat different cancers and in some, severe cases, it can be used for rheumatoid arthritis.

There are other medications which can help to manage your condition. There are other drugs which are used as chemotherapy as well as surgery and radiotherapy which are commonly used to treat different cancers. Your doctor will help you to decide the best course of treatment for you.

Cytoxan is one of several drugs that may be used to manage your condition. You can discuss the effectiveness and expected results of treatment with your doctor.

Your doctor will continue to carry out blood tests and scans depending on your condition to determine if the medication is working. Adjustments to your dose or a change in frequency may be advised by your doctor based on these results.

No, it should not be used in pregnancy as it causes harm to the pregnancy. You should use effective contraception during treatment and for at least three months after your treatment has finished. This applies to both men and women being treated with Cytoxan. If you are already pregnant or become pregnant, you should discuss the risks and benefits with your doctor. Cytoxan can lead to interference of the menstrual cycle in women and can stop sperm production in men. It can cause permanent infertility. However, you should not assume that you cannot become pregnant or that you cannot get someone else pregnant.

No, it should not be used if breastfeeding as it enters breast milk and will be harmful to your child. Breast feeding should be stopped if receiving this treatment. You should discuss this with your doctor.

If you think that you or someone else has taken an overdose of Cytoxan, contact your doctor immediately. Symptoms such as rapid heart rate, breathing difficulties, stomach pain, mouth sores, weight gain, and yellowing of the skin and eyes may be seen. Other symptoms include black, tarry stools, red urine, unusual bruising or bleeding, unusual tiredness or weakness, fever, and chest pain.

If you or someone else has collapsed or stopped breathing after taking Cytoxan, call the emergency services.

You should drink lots of fluids while taking Cytoxan, as it can cause problems if urine containing the drug is left in your bladder for a prolonged period. It is recommended that you drink 10 – 12 cups of fluid each day and urinate regularly to empty your bladder.

Contact your doctor as soon as possible to discuss the best course of action if a dose is missed. The medication will not be as effective. For Cytoxan to work effectively, a certain amount must be in your body at all times. Receiving your dose as your doctor has scheduled will help to treat your cancer and aims to prevent recurrence or spread to other parts of your body.

This is a prescription medicine. Do not give to others even if they have similar symptoms. Consult your doctor before starting or stopping any medications.

If you have any questions or concerns regarding use of this medication you can discuss these with your doctor, pharmacist or healthcare provider.