Cladribine
Say it: KLAD-rih-been
Cladribine is a chemotherapy medicine that kills certain blood cancer cells by blocking how they make DNA.
What it is
Cladribine looks like one of the building blocks of DNA. White blood cells called lymphocytes take it in and build it into their DNA by mistake. This damages the cells and they die.
Often used for
- hairy cell leukemia
- some other leukemias and lymphomas
- Langerhans cell histiocytosis
How you get it
Cladribine is given through a vein (IV) or as a shot under the skin. For hairy cell leukemia it is often given as one course, either as a slow drip around the clock for 7 days or as a daily dose for about 5 days. Many people only need one course. Your schedule may be different.
Common side effects and what helps
- Fever, often in the first weeks, even without an infection. Still call your team for any fever.
- Low blood counts, which raise your risk of infection and bleeding. Wash your hands often.
- Feeling tired. Rest and short walks can help.
- Rash. Tell your team if it spreads or blisters.
- Nausea and less appetite. Small meals may help.
- Headache. Ask your team what pain medicine is safe.
Call your care team right away if you have
- A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, or chills
- Cough, shortness of breath, or other signs of infection
- Unusual bleeding or bruising
- Numbness, weakness, or tingling in your arms or legs
- Making much less urine than usual, or swelling in your legs
- A skin rash with blisters or peeling
Before you start, tell your team
- If you are pregnant, may become pregnant, or are breastfeeding
- If you have kidney problems
- If you have an infection now, or have had shingles or hepatitis
- If you need a blood transfusion soon
- All the medicines, vitamins, and herbal products you take
Good to know
- Cladribine lowers blood counts for weeks to months. You will have blood tests often.
- Your immune system stays weak for a long time after treatment. Your team may give medicines to prevent certain infections. If you need a blood transfusion, the blood may need to be specially treated (irradiated).
- At high doses it can harm the nerves and kidneys. Your team will check your kidney blood tests.
- Ask your team before getting any live vaccine.
At home
- If you go home with a pump, keep it dry and do not disconnect it yourself. Call your team if it alarms or leaks.
Questions to ask
- How many days of treatment will I need?
- Will I need medicines to prevent infection, and for how long?
- Do I need special blood if I get a transfusion?
- When will we know if the treatment worked?
Part of these treatment plans
Side effect guides
- Fatigue (tiredness)
- Nausea and vomiting
- Appetite loss and weight loss
- Low white blood cells and infection risk
- Low platelets and bleeding
- Skin rash (including EGFR-inhibitor rash)
- Pain
Sources
Quick answers
- What is Cladribine?
- Cladribine is a chemotherapy medicine that kills certain blood cancer cells by blocking how they make DNA.
- What is Cladribine used for?
- hairy cell leukemia; some other leukemias and lymphomas; Langerhans cell histiocytosis.
- How is Cladribine given?
- Cladribine is given through a vein (IV) or as a shot under the skin. For hairy cell leukemia it is often given as one course, either as a slow drip around the clock for 7 days or as a daily dose for about 5 days. Many people only need one course. Your schedule may be different.
- What are the common side effects of Cladribine?
- Fever, often in the first weeks, even without an infection. Low blood counts, which raise your risk of infection and bleeding. Feeling tired. Rash. Nausea and less appetite. Headache.
- When should I call my care team while taking Cladribine?
- A fever of 100.4 degrees Fahrenheit (38 degrees Celsius) or higher, or chills; Cough, shortness of breath, or other signs of infection; Unusual bleeding or bruising; Numbness, weakness, or tingling in your arms or legs; Making much less urine than usual, or swelling in your legs; A skin rash with blisters or peeling.
- Which chemotherapy plans include Cladribine?
- CLAG-M.
Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.