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Janus Kinase (JAK) Inhibitors

Janus Kinase (JAK) Inhibitors

JAK inhibitors are a new class of arthritis drugs that treat rheumatoid arthritis. They’re not biologics. They are known as small molecule medications.

JAK inhibitors come in pill form. They decrease your immune system’s ability to make certain enzymes that can lead to RA symptoms.

JAK inhibitors can be used with or without methotrexate. Your rheumatologist may even prescribe this drug before you try a biologic if he or she thinks it’s the right option for you.

Tofacitinib (Xeljanz ®), Baricitinib (Olumiant ®), Upadacitinib (Rinvoq ®)

Your doctor may prescribe these JAK inhibitors if you are not able to tolerate methotrexate, or if you have taken methotrexate without any result. You may be taking a JAK inhibitor alone or in combination with another drug. These work by decreasing the effectiveness of the immune system to reduce pain, swelling, and inflammation.

JAK inhibitors come in tablet form. It can be taken once or twice a day, usually without food. It is a good idea to read the label carefully and talk with your doctor to make sure you fully understand how to take your medication.

With JAK inhibitors, you may start to see an improvement in your symptoms in as little as two weeks. However, it typically takes up to three to six months to reach full effectiveness.

Talk to your doctor if you experience any of the following:

  • Negative reactions or side effects
  • Concerns about why you have been prescribed this drug
  • Your symptoms do not improve within six months
  • Questions or confusion about your medication usage
  • If you are planning surgery
  • If you are planning on missing your dose for any reason
  • Possible signs of an infection like chills or nausea
  • Fever
  • If you may be pregnant

Side Effects of JAK inhibitors

Many patients do not experience side effects, and those who do rarely experience serious side effects. Many side effects become less serious and frequent over time. Some less serious side effects include:

  • Nausea
  • Indigestion
  • Diarrhea
  • Headaches
  • Upper respiratory tract infection
  • Increased cholesterol levels

In rare cases, more serious side effects can occur, such as:

  • Infection
  • Abnormal blood counts
  • Abnormal liver function tests
  • Increased risk of bowel perforation
  • Decrease in kidney function

Taking your medication as prescribed by your doctor, getting your blood regularly monitored, and attending all your medical appointments will reduce the occurrence and seriousness of any side effects.

How to Monitor for Side Effects

While you are taking JAK inhibitors, you will need to get periodic blood tests so your doctor can monitor different values. This is to ensure that the medication is working effectively and to keep track of whether or not there are any negative side effects.

Lymphocyte count: You’ll need this test once before you begin taking a JAK inhibitor to note your “baseline,” and then every three months after. Lymphocyte counts are used to measure your white blood cells. White blood cells are an important part of your immune system. Lymphocyte counts are used to determine whether or not the medication is working, and to make sure that your immune system can still prevent you from getting an infection. If your lymphocyte count is too low, your doctor may change your dosage or medication.

Neutrophil/platelet counts: You’ll need this test once to note your baseline, once after four to eight weeks, and every three months after. Neutrophil counts measure another type of white blood cells, and so they are monitored as another way to ensure your medication is working and not causing harm. Platelets are also a part of your immune system, but control your blood’s ability to clot. If you have too few, there is a risk for unusual bleeding. If your blood work shows too few platelets or neutrophils, your doctor may adjust your dosage or medication.

Hemoglobin: You’ll need this test once to note your baseline, once after four to eight weeks, and every three months after. Hemoglobin is a part of your red blood cells, and helps carry oxygen in your bloodstream. Too little hemoglobin can lead to increased abnormal bleeding. Monitoring can reveal whether or not you are at risk for bleeding, and if your hemoglobin is too low, your doctor may adjust your medication.

Lipids: You’ll need this test four to eight weeks after you begin taking the medication and periodically afterward. Lipid levels are measured to ensure that the JAK inhibitor you are taking is not having a negative effect on your cholesterol levels.

LFTs: LFTs, or Liver Function Tests, should be done periodically to ensure that liver damage does not occur.

Viral Hepatitis: Prior to starting your medication, you should be tested for viral hepatitis. You should not take this drug if you are positive for viral hepatitis.

You will also need to have your heart rate and blood pressure periodically monitored, as well as skin tests, and signs and symptoms of any potential infections. This is to ensure that you’re not having any negative side effects. If you have any potential harmful impacts from taking this drug, your doctor may adjust your dosage or medication.

JAK inhibitor Contraindications

Contraindications for JAK inhibitors are: having a history of a reaction to another JAK inhibitor, pregnancy, some liver disease, some kidney disease, blood disorders, some cancers, active infections, or a history of active tuberculosis.

JAK inhibitor Comorbidities

Talk with your doctor if you have any of these comorbidities: chronic respiratory conditions, diabetes, heart disease, or stroke. In some cases, medications to treat them may interact with the JAK inhibitor, and it is important your doctor is giving you the proper treatments.