Busulfan (Myleran, Busilvex) | Cancer Research UK
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Busulfan (Myleran, Busilvex)

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This page tells you about the chemotherapy drug busulfan and its possible side effects. There are sections about


What busulfan is

Busulfan is a chemotherapy drug most often given as low dose treatment for a long time to treat chronic myeloid leukaemia. Or you may have it in higher doses before a bone marrow or stem cell transplant for other types of cancer and leukaemia. 

Busulfan tablets are called Myleran and the injections are called Busilvex. Busulfan is an alkylating agent, which works by sticking to one of the cancer cell's DNA strands. The cell cannot then divide into 2 new cells.


How you have busulfan

Busulfan comes in 2mg white tablets, 25mg capsules and as a clear liquid given by injection into a vein.

It is very important that you take tablets or capsules according to the instructions your doctor or pharmacist gave you. Whether you have a full or empty stomach, for example, can affect how much of a drug gets into your bloodstream. You should take the right dose, not more or less. And never stop taking a cancer drug without talking to your specialist first.

You usually have busulfan as a course of several cycles of treatment. The exact treatment plan depends on which type of leukaemia you have. There is detailed information about chemotherapy treatment planning in our planning chemotherapy section.

We've listed the side effects associated with busulfan below. You can click on the links to find out more about each side effect. Where there is no link please see our cancer drug side effects section or use the search box at the top of the page.


Common side effects

More than 10 in every 100 people have one or more of the side effects listed below.

  • An increased risk of getting an infection from a drop in white blood cells – it is harder to fight infections and you can become very ill. You may have headaches, aching muscles, a cough, a sore throat, pain passing urine, or you may feel cold and shivery. If you have a severe infection this can be life threatening. Contact your treatment centre straight away if you have any of these effects or if your temperature goes above 38°C. You will have regular blood tests to check your blood cell levels
  • Tiredness and breathlessness due to a drop in red blood cells (anaemia) – you may need a blood transfusion
  • Bruising more easily due to a drop in platelets – you may have nosebleeds, bleeding gums after brushing your teeth, or lots of tiny red spots or bruises on your arms or legs (known as petechia).
  • Tiredness and weakness (fatigue) during and after treatment – most people find their energy levels are back to normal within 6 months to a year
  • Feeling or being sick is rare with low dose treatment, but common with higher doses (especially before a bone marrow or stem cell transplant). Taking busulfan tablets or capsules on an empty stomach may help
  • Loss of appetite is rare with low dose treatment but common with higher doses
  • Women may stop having periods (amenorrhoea) but this may only be temporary
  • Loss of fertility may happen with this drug – you may not be able to become pregnant or father a child after treatment with this drug. Talk to your doctor before starting treatment if you think you may want to have a baby in the future. Men may be able to store sperm before starting treatment

Occasional side effects

Between 1 and 10 in every 100 people have one or more of these.

  • Hair loss – this is rare with low doses but can happen with high dose treatment
  • A sore mouth is rare with low dose treatment, but can be severe with high doses. Tell your doctor or nurse if you have this as you can take painkillers and use mouthwashes to help
  • Skin changes – you may get an itchy rash or your skin may darken in places, particularly your hands and nail beds
  • Diarrhoea is rare with low doses, but can happen with high dose treatment. Drink plenty of fluids and tell your doctor or nurse if diarrhoea becomes severe, or continues for more than 3 days

Rare side effects

Fewer than 1 in 100 people have these effects.

  • Lung problems – you may have a cough or wheezing, which can happen straight away or up to 10 years after your treatment
  • Fits (seizures) with high dose treatment – your doctor will give you tablets to prevent this
  • Liver changes – you will have blood tests to check for this
  • Difficulty sleeping, dizziness, or depression can happen with high dose treatment – tell your doctor or nurse about this
  • An increased risk of developing another cancer in the future after treatment with busulfan
  • Soreness, tenderness and swelling of the breasts
  • Cataracts of the eye, causing blurred or cloudy vision

Important points to remember

The side effects above may be mild or more severe. A side effect may get better or worse through your course of treatment, or more side effects may develop as the course goes on. This depends on

  • How many times you've had the drug before
  • Your general health
  • The amount of the drug you have (the dose)
  • Other drugs you are having

Coping with side effects

Talk to your doctor, pharmacist or nurse about all your side effects so they can help you manage them. They can give you advice or reassure you. Your nurse will give you a contact number to ring if you have any questions or problems. If in doubt, call them.

Other medicines

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and over the counter remedies. Some drugs can react together.

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant or father a child while you are having treatment and for a few months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.


Do not breastfeed during this treatment because the drug may come through in the breast milk.


Immunisations and chemotherapy

You should not have immunisations with live vaccines while you are having chemotherapy or for at least 6 months afterwards. In the UK, these include rubella, mumps, measles (usually given together as MMR), BCG, yellow fever and Zostavax (shingles vaccine).

You can have other vaccines, but they may not give you as much protection as usual until your immune system has fully recovered from your chemotherapy. It is safe to have the flu vaccine.

It is safe for you to be in contact with other people who've had live vaccines as injections. There can be problems with vaccines you take by mouth (oral vaccines), but not many people in the UK have these now. So there is usually no problem in being with any baby or child who has recently had any vaccination in the UK. You might need to make sure that you aren't in contact with anyone who has had oral polio, cholera or typhoid vaccination recently, particularly if you live abroad.


Related information 


More information about busulfan

This page does not list all the very rare side effects of this treatment that are very unlikely to affect you. For further information look at the Electronic Medicines Compendium website at www.medicines.org.uk.

If you have a side effect not mentioned here that you think may be due to this treatment you can report it to the Medicines Health and Regulatory Authority (MHRA) at www.mhra.gov.uk.

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Updated: 2 July 2014