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What are the possible risks and side-effects of cyclophosphamide?

A common side-effect of cyclophosphamide is feeling sick (nausea). Your doctor may prescribe medicine to control this.

Because cyclophosphamide affects your immune system, it can make you more likely to pick up infections. It can also make them harder to spot. Make sure you have your repeat blood tests and tell your doctor or rheumatology nurse straight away if you develop:

  • a sore throat, fever or other signs of infection
  • unexplained bruising or bleeding
  • any other new symptoms that concern you.

You should stop taking cyclophosphamide, try to get a prompt blood test, and see your doctor immediately if any of the above symptoms are severe.

You should also see your doctor if you get chickenpox or shingles or come into contact with someone who has chickenpox or shingles. These illnesses can be severe if you're on cyclophosphamide. You may need antiviral treatment, and your cyclophosphamide may need to be stopped until you're better.

One very important side-effect is inflammation and bleeding of the bladder wall (haemorrhagic cystitis). If this happens you may notice blood in your urine and you must see your doctor immediately. To reduce the risk of this happening, you should drink 8–10 glasses (2–3 litres) of non-alcoholic drinks or water a day. You may be prescribed a drug called mesna to try to reduce the risk of cystitis.

Cyclophosphamide can also affect the blood count, which means your body is making fewer blood cells.

Because cyclophosphamide can affect the blood and the bladder, your doctor will arrange for you to have blood and urine tests before and during treatment. You may be asked to keep a record of your test results in a booklet and to bring it with you when you visit your GP or the hospital.

You must not take cyclophosphamide unless you're having regular checks.

Sometimes cyclophosphamide can cause hair loss, mouth ulcers and irregular menstrual periods.

There's a slightly increased risk of certain types of cancer, particularly bladder cancer, but cyclophosphamide won't be prescribed unless your doctor thinks the benefits outweigh the risks.

Reducing the risk of infection

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