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Side Effects of
JAK Inhibitors


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Janus kinase inhibitors, also known as JAK inhibitors, are a newer class of drugs that are beneficial in treating immune mediated diseases, such as rheumatoid arthritis, inflammatory bowel disease and psoriasis, as well as preventing transplant rejection. Medical research determined that JAKs play an important role in immune defense, eventually leading to the discovery of these drugs. The JAK inhibitors that are on the market include ruxolitinib (Jakafi) and tofacitinib (Xeljanz). (Immunology Review “Therapeutic targeting of Janus kinases,” Jun 2008).

Serious Side Effects of JAK Inhibitors

Severe side effects of JAK Inhibitors include liver damage, neutropenia and lymphopenia (dangerously low white cell counts and immune system suppression). Additionally, JAK inhibitors may interact with DMARDs (disease modifying anti-rheumatic drugs) or with other immunosuppressants. (Annals of the Rheumatic Diseases “Janus kinase inhibitors in autoimmune diseases,” Apr 2013).

Common Side Effects

Common side effects include upper respiratory infections, diarrhea, headache and cold symptoms such as sore throat, runny or stuffy nose, dizziness, headache, bruising, urinary tract infections, weight gain, bloating, gas, low blood platelet levels, anemia, fatigue, diarrhea, and shortness of breath. (Annals of the Rheumatic Diseases “Janus kinase inhibitors in autoimmune diseases,” Apr 2013).

Understand Your Risks with the Rxight® Genetic Test

Rxight® pharmacogenetic testing from MD Labs can determine how well you metabolize hundreds of clinically relevant OTC and prescription medications across nearly 50 medication classes, including JAK inhibitors – and therefore how prone you are to side effects or to medication inefficacy – in one simple, non-invasive. DNA sample from a cheek swab. After your sample is sent to our lab for analysis, the results will be reviewed with you in detail. This means that preferably prior to taking any new drug, you and your physician can use the results of the Rxight® test to make the wisest choices about your medications. And you have your lifelong “medication blueprint” for any future medication treatment.

How Does Pharmacogenetic Testing Work?

Pharmacogenetics is the study of how inter-interindividual variations in the genes impacts how the enzymes for which they encode metabolize drugs. Typically, in the absence of genetic testing, the traditional way for providers to determine your drug adverse reactions is to use the trial and error approach to prescribing medications. However, with the sequencing of the human genome, individual genetic variation in drug metabolism genes can predict how a patient will respond to a pharmacological agent. Variation in any of these genes means that the enzyme made from the genetic instructions is also altered, resulting in side effects that would be unpredictable with the traditional approach of trial and error.

Contributors to this Article:
Michael Sapko, MD, PhD; Deborah Kallick, PhD, Medicinal Chemistry

JAK Inhibitors Tested Include:

Read more about Rxight® DNA Drug Testing Swabbing Mouth