Jakafi can cause serious side effects, including:
Low blood counts: Jakafi® (ruxolitinib) may cause low platelet, red blood cell, and white blood cell counts. If you develop bleeding, stop taking Jakafi and call your healthcare provider. Your healthcare provider will do a blood test to check your blood counts before you start Jakafi and regularly during your treatment. Your healthcare provider may change your dose of Jakafi or stop your treatment based on the results of your blood tests. Tell your healthcare provider right away if you develop or have worsening symptoms such as unusual bleeding, bruising, tiredness, shortness of breath, or a fever.
Infection: You may be at risk for developing a serious infection during treatment with Jakafi. Tell your healthcare provider if you develop any of the following symptoms of infection: chills, nausea, vomiting, aches, weakness, fever, painful skin rash or blisters.
Cancer: Some people have had certain types of non-melanoma skin cancers during treatment with Jakafi. Your healthcare provider will regularly check your skin during your treatment with Jakafi. Tell your healthcare provider if you develop any new or changing skin lesions during treatment with Jakafi.
Increases in cholesterol: You may have changes in your blood cholesterol levels during treatment with Jakafi. Your healthcare provider will do blood tests to check your cholesterol levels about every 8 to 12 weeks after you start taking Jakafi, and as needed.
Increased risk of major cardiovascular events such as heart attack, stroke or death in people who have cardiovascular risk factors and who are current or past smokers while using another JAK inhibitor to treat rheumatoid arthritis: Get emergency help right away if you have any symptoms of a heart attack or stroke while taking Jakafi, including: discomfort in the center of your chest that lasts for more than a few minutes, or that goes away and comes back, severe tightness, pain, pressure, or heaviness in your chest, throat, neck, or jaw, pain or discomfort in your arms, back, neck, jaw, or stomach, shortness of breath with or without chest discomfort, breaking out in a cold sweat, nausea or vomiting, feeling lightheaded, weakness in one part or on one side of your body, slurred speech
Increased risk of blood clots: Blood clots in the veins of your legs (deep vein thrombosis, DVT) or lungs (pulmonary embolism, PE) have happened in people taking another JAK inhibitor for rheumatoid arthritis and may be life-threatening. Tell your healthcare provider right away if you have any signs and symptoms of blood clots during treatment with Jakafi, including: swelling, pain, or tenderness in one or both legs, sudden, unexplained chest or upper back pain, shortness of breath or difficulty breathing
Possible increased risk of new (secondary) cancers: People who take another JAK inhibitor for rheumatoid arthritis have an increased risk of new (secondary) cancers, including lymphoma and other cancers. People who smoke or who smoked in the past have an added risk of new cancers.
The most common side effects of Jakafi include: for certain types of myelofibrosis (MF) and polycythemia vera (PV) – low platelet or red blood cell counts, bruising, dizziness, headache, and diarrhea; for acute GVHD – low platelet counts, low red or white blood cell counts, infections, and swelling; and for chronic GVHD – low red blood cell or platelet counts and infections including viral infections.
These are not all the possible side effects of Jakafi. Ask your pharmacist or healthcare provider for more information. Call your doctor for medical advice about side effects.
Before taking Jakafi, tell your healthcare provider about: all the medications, vitamins, and herbal supplements you are taking and all your medical conditions, including if you have an infection, have or had low white or red blood cell counts, have or had tuberculosis (TB) or have been in close contact with someone who has TB, had shingles (herpes zoster), have or had hepatitis B, have or had liver or kidney problems, are on dialysis, have high cholesterol or triglycerides, had cancer, are a current or past smoker, had a blood clot, heart attack, other heart problems or stroke, or have any other medical condition. Take Jakafi exactly as your healthcare provider tells you. Do not change your dose or stop taking Jakafi without first talking to your healthcare provider.
Women should not take Jakafi while pregnant or planning to become pregnant. Do not breastfeed during treatment with Jakafi and for 2 weeks after the final dose.
Please see the Full Prescribing Information, which includes a more complete discussion of the risks associated with Jakafi.
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit www.fda.gov/medwatch, or call 1-800-FDA-1088.
You may also report side effects to Incyte Medical Information at 1-855-463-3463.
- Symptoms
- Causes
- Risk factors
- Diagnosis
- Treatment
- Complications
- Outlook
What is myelofibrosis?
Myelofibrosis (MF) is a type of bone marrow cancer that affects your body’s ability to produce blood cells. It’s part of a group of conditions called myeloproliferative neoplasms (MPNs). These conditions cause your bone marrow cells to stop developing and functioning the way they should, resulting in fibrous scar tissue.
MF can be primary, meaning it occurs on its own, or secondary, meaning it results from another condition — usually one that affects your bone marrow. Other MPNs can also progress to MF. While some people can go years without having symptoms, others have symptoms that get worse due to scarring in their bone marrow.
Myelofibrosis tends to come on slowly, and many people don’t notice symptoms at first. However, as it progresses and starts to interfere with blood cell production, its symptoms may include:
- fatigue
- shortness of breath
- bruising or bleeding easily
- feeling pain or fullness on your left side, below your ribs
- night sweats
- fever
- bone pain
- loss of appetite and weight loss
- nosebleeds or bleeding gums
Myelofibrosis is associated with a genetic mutation in blood stem cells. However, researchers aren’t sure what causes this mutation.
When the mutated cells replicate and divide, they pass the mutation on to new blood cells. Eventually, the mutated cells overtake the bone marrow’s ability to produce healthy blood cells. This usually results in too few red blood cells and too many white blood cells. It also causes scarring and hardening of your bone marrow, which is usually soft and spongy.
Myelofibrosis is rare, occurring in only about 1.5 out of every 100,000 people in the United States. However, several things can increase your risk of developing it, including:
- Age. While people of any age can have myelofibrosis, it’s usually diagnosed in those over the age of 50.
- Another blood disorder. Some people with MF develop it as a complication of another condition, such as thrombocythemia or polycythemia vera.
- Exposure to chemicals. MF has been associated with exposure to certain industrial chemicals, including toluene and benzene.
- Exposure to radiation. People who’ve been exposed to radioactive material may have an increased risk of developing MF.
MF usually shows up on a routine complete blood count (CBC). People with MF tend to have very low levels of red blood cells and unusually high or low levels of white blood cells and platelets.
Based on the results of your CBC test, your doctor might also do a bone marrow biopsy. This involves taking a small sample of your bone marrow and looking at it more closely for signs of MF, such as scarring.
You may also need an X-ray or MRI scan to rule out any other potential causes of your symptoms or CBC results.
MF treatment usually depends on the types of symptoms you have. Many common MF symptoms are associated with an underlying condition caused by MF, such as anemia or an enlarged spleen.
Treating anemia
If MF is causing severe anemia, you may need:
- Blood transfusions. Regular blood transfusions can increase your red blood cell count and reduce anemia symptoms, such as fatigue and weakness.
- Hormone therapy. A synthetic version of the male hormone androgen may promote red blood cell production in some people.
- Corticosteroids. These may be used with androgens to encourage red blood cell production or decrease their destruction.
- Prescription medications. Immunomodulatory medications, such as thalidomide (Thalomid), and lenalidomide (Revlimid), may improve blood cell counts. They may also help with symptoms of an enlarged spleen.
Treating an enlarged spleen
If you have an enlarged spleen related to MF that’s causing problems, your doctor might recommend:
- Radiation therapy. Radiation therapy uses targeted beams to kill cells and reduce the size of the spleen.
- Chemotherapy. Some chemotherapy drugs may reduce the size of your enlarged spleen.
- Surgery. A splenectomy is a surgical procedure that removes your spleen. Your doctor might recommend this if you aren’t responding well to other treatments.
Treating mutated genes
A new drug called ruxolitinib (Jakafi) was approved by the U.S. Food and Drug Administration in 2011 to treat the symptoms associated with MF. Ruxolitinib targets a specific genetic mutation that may be the cause of MF. In clinical trials, it was shown to reduce the size of enlarged spleens, reduce the symptoms of MF, and improve prognosis.
Experimental treatments
Researchers are working on developing new treatments for MF. While many of these require further study to make sure they’re safe, doctors have started using two new treatments in certain cases:
- Stem cell transplant. Stem cell transplants have the potential to cure MF and restore bone marrow function. However, the procedure can cause life-threatening complications, so it’s usually only done when nothing else works.
- Interferon-alpha. Interferon-alfa has delayed the formation of scar tissue in the bone marrow of people who receive treatment early on, but more research is needed to determine its long-term safety.
Over time, myelofibrosis can lead to several complications, including:
- Increased blood pressure in your liver. Increased blood flow from an enlarged spleen can raise the pressure in the portal vein in your liver, causing a condition called portal hypertension. This can put too much pressure on smaller veins in your stomach and esophagus, which could lead to excessive bleeding or a ruptured vein.
- Tumors. Blood cells can form in clumps outside the bone marrow, causing tumors to grow in other areas of your body. Depending on where these tumors are located, they can cause a variety of different problems, including seizures, bleeding in the gastric tract, or compression of the spinal cord.
- Acute leukemia. About 15 to 20 percent of people with MF go on to develop acute myeloid leukemia, a serious and aggressive form of cancer.
While MF often doesn’t cause symptoms in its early stages, it can eventually lead to serious complications, including more aggressive types of cancer. Work with your doctor to determine the best course of treatment for you and how you can manage your symptoms. Living with MF can be stressful, so you may find it helpful to seek out support from an organization such as the Leukemia and Lymphoma Society or the Myeloproliferative Neoplasm Research Foundation. Both organizations can help you find local support groups, online communities, and even financial resources for treatment.
Last medically reviewed on February 13, 2018