A purine-analogue chemotherapy, also used in multiple sclerosis
Cladribine
A medicine used to treat hairy-cell leukaemia and some other blood cancers, and separately for relapsing multiple sclerosis.
What is Cladribine?
Cladribine is a specialist medicine of a type called a purine analogue. It is used to treat hairy-cell leukaemia and some other blood cancers, and in a separate tablet form to treat relapsing multiple sclerosis. It works by damaging the DNA of certain white blood cells, lowering the cells that drive these conditions. For the blood-cancer uses it is usually given as an injection or drip; for multiple sclerosis it is given as tablets in short courses. Its most important effects are a long-lasting drop in immune cells that raises the risk of serious infections, a fall in other blood cells, and over the long term a small added risk of a second cancer. It can harm an unborn baby, so contraception is essential.
Education and reference only. This is a plain-language guide to Cladribine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Cladribine is a medicine that works like a building block of DNA, which is why it is called a purine analogue. It has two main roles. As a chemotherapy, it treats hairy-cell leukaemia and some other blood cancers, usually given as an injection under the skin or as a drip into a vein. In a separate tablet form, it is used to treat relapsing multiple sclerosis, where it is taken in short courses spread over a couple of years. In both uses it works by reducing certain white blood cells, and it is always prescribed and supervised by a specialist team.
How it works
Cladribine is taken up by certain white blood cells, particularly lymphocytes, where it interferes with their DNA and causes them to die. In blood cancers such as hairy-cell leukaemia, this lowers the abnormal cancerous cells. In multiple sclerosis, it reduces the immune cells that mistakenly attack the nervous system, calming the disease. Because it strongly lowers lymphocytes, the cells that fight infection, this effect can last a long time after treatment, which is why protecting against infection and monitoring blood counts are so important.
Company & origin
Originated / developed by: Specialist manufacturers.
A specialist medicine used in the UK to treat hairy-cell leukaemia and some other blood cancers, and in a separate tablet form for relapsing multiple sclerosis.
Practical use
How to take Cladribine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Follow your specialist's plan: for blood cancers it is usually given as an injection or drip, while for multiple sclerosis it is taken as tablets in short courses.
- Report any fever, chills or sign of infection straight away, as your infection-fighting cells stay low for a long time.
- Attend all your blood tests, as your blood counts guide treatment and follow-up.
- Avoid live vaccines and tell any healthcare professional you have had cladribine, as your immune system stays affected.
- Use reliable contraception during treatment and for the time your team advises, as it can harm an unborn baby, for both women and men.
Weighing it up
Advantages & disadvantages of Cladribine
Advantages
- An effective treatment for hairy-cell leukaemia, often giving long-lasting control.
- In tablet form, offers short courses of treatment for relapsing multiple sclerosis spread over time.
- Works by lowering specific white blood cells that drive these conditions.
Disadvantages
- Causes a long-lasting drop in immune cells, raising the risk of serious infections.
- Lowers other blood cells, causing tiredness, bruising or bleeding.
- Over the long term, carries a small added risk of a second cancer.
Practical use
Good to know
The most important thing to understand is that cladribine causes a long-lasting drop in lymphocytes, the immune cells that fight infection, so the risk of serious infections, including unusual ones and reactivation of old infections, can persist for a long time; any fever or sign of infection needs prompt attention. It also lowers other blood cells, causing tiredness, bruising or bleeding, so blood counts are checked regularly. Over the long term, treatments that affect DNA and the immune system can slightly raise the risk of a second cancer, so ongoing follow-up matters. Screening for infections such as tuberculosis, hepatitis and others is often done before treatment, and live vaccines are avoided. Because it can seriously harm an unborn baby, reliable contraception during and after treatment is essential for both women and men.
Who should not take it / use with caution
- People who have had a serious allergic reaction to cladribine should not receive it.
- It is not used in pregnancy because it can seriously harm an unborn baby, and breastfeeding is avoided.
- It is generally avoided in people with active serious infections, certain cancers, or, for the multiple sclerosis form, in those whose immune system is already significantly weakened, under specialist judgement.
Monitoring
- Regular blood counts, including the immune cells, before, during and after treatment.
- Screening for infections such as tuberculosis and hepatitis before treatment, and watching for infection afterwards.
- Long-term follow-up for late effects, including any signs of a second cancer.
Side effects
- A long-lasting fall in immune cells, raising the risk of serious or unusual infections.
- A fall in other blood cells, causing tiredness, a higher risk of infection and easier bruising or bleeding.
- Fever, nausea, headache or, with injections, reactions where it is given.
- Rarely but seriously, severe infections, reactivation of old infections, or a second cancer over the long term.
Key interactions
- It is used with care alongside other medicines that lower blood cells or weaken the immune system.
- Live vaccines are avoided because the immune system is weakened for a long time.
- Other medicines that affect immune cells may add to the risk of infection, so give a full medicines list.
Available as: A solution given as an injection under the skin or a drip into a vein, and separately tablets for multiple sclerosis.
Answers
Cladribine: frequently asked questions
What is cladribine used for?
It is used to treat hairy-cell leukaemia and some other blood cancers, and in a separate tablet form to treat relapsing multiple sclerosis.
Why does my infection risk stay high for so long?
It causes a long-lasting drop in lymphocytes, the immune cells that fight infection, so the risk of serious infections can persist well after treatment, and any fever needs prompt attention.
How is it given?
For blood cancers it is usually given as an injection under the skin or a drip into a vein; for multiple sclerosis it is taken as tablets in short courses spread over time.
Can I have my usual vaccinations?
Live vaccines are avoided because the immune system stays weakened for a long time; ask your team for advice on which vaccines are safe and when.
Can I be treated while trying for a baby?
No. Cladribine can seriously harm an unborn baby, so reliable contraception is essential during and after treatment for both women and men.
Authoritative sources
- BNF
- NICE CKS
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