Ruxolitinib is a targeted therapy that is used to treat some types of myeloproliferative neoplasms (MPNs). These are conditions that affect how blood cells are made.

How ruxolitinib works

Ruxolitinib is a type of drug called a protein kinase inhibitor.

Genes called JAK1 and JAK2 help control the number of blood cells the body makes. If either of these genes become faulty, the body may make too many blood cells. Ruxolitinib blocks (inhibits) the signals that are sent by the faulty gene. This helps reduce the number of extra blood cells that are made.

Ruxolitinib can block other signals that cause too many blood cells to be made. So it can also work for people who do not have a faulty JAK gene.

When ruxolitinib is used

Ruxolitinib may be used to treat:

  • myelofibrosis
  • polycythaemia vera.

Myelofibrosis (MF) is a condition that affects the bone marrow (where blood cells are made). In MF, scar tissue builds up inside the bone marrow and blood cells are not made properly.

MF can cause symptoms such as:

  • tiredness
  • high temperatures
  • night sweats
  • itching
  • weight loss
  • bone pain.

It can also cause the spleen to get bigger. The spleen is on the left side of the tummy under the ribs. It helps break down blood cells. Symptoms of an enlarged spleen include discomfort on the left side of the tummy and quickly feeling full when eating.

If you have MF and your spleen is too big, or you have other symptoms, you may be given ruxolitinib. It can help reduce the size of the spleen and relieve symptoms.

Polycythaemia vera (PV) is a condition which causes the body to make too many red blood cells.

If you have you PV, and the drug hydroxycarbamide (or hydroxyurea) is not working or is causing side effects), you may be given ruxolitinib.

Ruxolitinib may only be available in certain situations. Your doctor can tell you if it is appropriate for you. Some people may be given it as part of a clinical trial. If a drug is not available on the NHS, there may be different ways you are still able to have it. Your doctor can give you advice. We have further information on what to do if your treatment is not available.

Taking ruxolitinib

Always take your tablets exactly as your doctor or nurse has told you to.

You should take ruxolitinib at the same time each day. Your doctor or nurse will tell you how often to take it. Take it with a glass of water, with or without food.

The dose you start on depends on the results of your blood tests and which condition you have. Your doctor may need to change this dose throughout your treatment. They will decide this by checking your blood tests regularly when you visit the hospital.

You will usually continue taking the drug for as long as it keeps the condition under control. It is important that you do not stop taking it without talking to your doctor first. Stopping the drug suddenly can make you feel unwell. Doctors usually gradually reduce your dose before stopping it completely to help with this.

There are some important points to remember about taking and storing your medication:

  • If you forget to take your tablet, wait and take your next dose at the right time. Do not take a double dose.
  • Avoid taking your tablet with grapefruit or Seville oranges, as they can affect how the drug works.
  • Keep the tablets in their original package.
  • Store them at room temperature (not over 30°C) and away from heat.
  • Keep them safe and out of the sight and reach of children.
  • If your treatment is stopped, return any remaining tablets to the pharmacist.

About side effects

Serious and life threatening side effects

Sometimes cancer drugs can result in very serious side effects, which rarely may be life threatening. Your doctor and nurse can explain the risk of these side effects to you.

Contact the hospital

Your nurse will give you telephone numbers for the hospital. You can call them if you feel unwell or need advice any time of day or night. Save these numbers in your phone or keep them somewhere safe.

More information about this drug

You may get some of the side effects we mention, but you are very unlikely to get them all. We are not able to list every side effect for this treatment here, particularly the rarer ones. For more detailed information you can visit the electronic Medicines Compendium (eMC).

Your doctor can prescribe drugs to help control some side effects. It is very important to take them exactly as your nurse or pharmacist has explained. Your nurse will give you advice about managing side effects. Always tell your doctor or nurse about the side effects you have.

Possible side effects

Effects on blood cells

You will have regular blood tests during treatment. If your blood cells levels are low, your doctor may delay your treatment for a short time or reduce the dose of ruxolitinib you are given.

Anaemia (low number of red blood cells)

This treatment can reduce the number of red blood cells in your blood. These cells carry oxygen around the body. If the number of red blood cells is low, you may be tired and breathless. Tell your doctor or nurse if you feel like this. If you are very anaemic, you may need a drip to give you extra red blood cells. This is called a blood transfusion.

Bleeding and bruising

Ruxolitinib may reduce the number of platelets in your blood. Platelets are cells that help the blood to clot.

Tell your doctor if you have any bruising or bleeding, especially if it appeared for no reason.

This includes nosebleeds, bleeding gums, blood spots or rashes on the skin. Tell your doctor if you are taking any medicines that may affect bleeding.

Ruxolitinib can sometimes cause more serious bleeding.

Contact the hospital straight away on the contact number you have been given if you:

  • have blood in your stools (bowel motions) or have black stools
  • vomit blood or have vomit that looks like coffee grounds
  • suddenly feel confused, muddled or drowsy
  • have weakness on one side of your body, slurred speech or changes in vision.

White blood cells (help prevent and fight off infection)

Ruxolitinib can reduce the number of white cells in your blood. This will make you more likely to get an infection. Your doctor will want to make sure that you do not have an infection before you start the treatment. Tell your doctor if you have ever had tuberculosis or have been in close contact with someone who has.

It is important to be aware of signs of possible infection.

Contact the hospital straight away on the contact number you have been given if:

  • your temperature goes over 37.5°C (99.5F) or over 38°C (100.4F), depending on the advice given by your doctor
  • you suddenly feel unwell, even with a normal temperature
  • you have symptoms of an infection – this can include feeling shaky, a sore throat, a cough, pain on passing urine, or needing to pass urine a lot.

Some people can get shingles while taking this drug. This is an infection of a nerve caused by the same virus that causes chickenpox. If you feel burning, tingling, numbness or itchiness in an area of your skin or develop a rash, let your doctor know straight away.

Rarely, some people taking this drug can develop an infection in the brain. This can make you feel confused or drowsy. Or it can cause weakness on one side of your body, slurred speech or changes in vision. If you or someone you know notices that you have any of these, contact the hospital straight away.


This treatment can cause you to feel dizzy and confused or unsteady. Tell your doctor or nurse straight away if you notice this. If you feel like this, do not drive or operate machinery.

Increased cholesterol levels

The drug can increase the cholesterol level in your blood. Your doctor can monitor this with blood tests.


This treatment can cause constipation. Here are some tips that may help:

  • Drink at least 2 litres (3½ pints) of fluids each day.
  • Eat high-fibre foods, such as fruit, vegetables and wholemeal bread.
  • Do regular gentle exercise, like going for short walks.

If you have constipation, contact the hospital for advice. Your doctor can give you drugs called laxatives to help.

Excess wind

Some people notice they pass more wind than usual when taking this drug. If you are affected, try to avoid food that you think gives you wind. Beans, pickles and fizzy drinks commonly cause problems.

Changes in the way your liver works

Ruxolitinib can affect how your liver works. You will have regular blood tests during treatment to check how well your liver is working. Some people may be given a lower dose of ruxolitinib if they have or have had liver problems.

Weight gain

Ruxolitinib may cause you to put on weight. Talk to your doctor if this happens.


This treatment may cause headaches. If this happens, tell your doctor or nurse. They can give you painkillers.

Increased blood pressure

This treatment can cause high blood pressure. You will have your blood pressure checked regularly. If you have headaches, nosebleeds or feel dizzy, let your doctor know. They can prescribe tablets to control high blood pressure.

If you have high blood pressure before you start treatment, your doctor will monitor you closely during treatment.

Risk of developing skin cancer (non-melanoma)

A small number of people taking ruxolitinib have developed skin cancer. Doctors are not sure if this is directly linked to taking ruxolitinib or for other reasons. Your doctor can talk through whether you might be at more risk. Tell your doctor if you notice any changes in your skin. Your doctor may recommend taking extra care in the sun.

Other information

Ruxolitinib and pregnancy

It is recommended that you do not become pregnant while taking ruxolitinib. This is because the drug might be harmful to a developing baby. It is important that women who could become pregnant use a reliable method of contraception while taking this drug.

You should not breastfeed while taking ruxolitinib. This is because doctors cannot be sure that your breast milk would not contain any of the drug.

Ruxolitinib and fertility

Doctors do not yet know if this drug will affect your ability to have children (fertility). If you are worried about this, you can talk to your doctor or nurse before treatment starts.

Ruxolitinib hepatitis B

If you have hepatitis B, taking ruxolitinib can affect this condition. Your doctor will monitor you while you are taking this drug. If you would like more information, talk to your doctor.

Taking other medication with ruxolitinib

There are several drugs, such as ciprofloxacin and fluconazole that can be harmful to take when you are taking ruxolitinib. Tell your doctor about any medicines you are taking, including over-the-counter drugs, complementary therapies and herbal drugs such as St John’s wort.

Ruxolitinib contains a small amount of lactose. If you have a lactose intolerance, talk to your doctor before you start taking this.

Medical and dental treatment

If you need to go into hospital for any reason, always tell the doctors and nurses that you are taking ruxolitinib. Explain you are taking tablets that no one should stop or restart without advice from your doctor. Give them contact details for your doctor.

Talk to your doctor or nurse if you think you need dental treatment. Always tell your dentist you are taking ruxolitinib before having any dental treatment.

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