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Side Effects of Tofacitinib (Xeljanz)


Side Effects of Tofacitinib (Xeljanz)

Tofacitinib, commonly known under the brand Xeljanz, is a Janus kinase (JAK) inhibitor. It is used primarily in the treatment of rheumatoid arthritis.

Common Side Effects

The common side effects of Xeljanz are:


  • Hypertension (high blood pressure)
  • Diarrhea
  • Anemia
  • Neutropenia (presence of low blood neutrophil concentration)
  • Lymphopenia (presence of low blood lymphocyte concentration)
  • AST and ALT elevation (usually a sign of liver damage)
  • Infections
  • Headache
  • Increased serum creatinine (suggestive of kidney damage)
  • Nasopharyngitis (inflammation of the nose, runny nose)


(Xeljanz label reported by the FDA).


Neutropenia and lymphopenia may become serious if not treated.

About Pharmacogenetic Testing

Xeljanz is metabolized in the cytochrome P450 enzyme superfamily, CYP2C19 and CYP3A4. Polymorphisms in these enzymes are likely to cause either increased or decreased probability of patients suffering from toxicity of the drug. As such, knowing whether patients hold polymorphisms in the enzymes CYP2C19 and CYP3A4 is highly beneficial for clinicians. Polymorphisms can determine whether a patient should be given a higher or lower dose of the drug, or possibly an entirely different drug altogether.

Know Your Risk with the Rxight® Genetic Test

MD Labs created Rxight® which tests these polymorphisms. Rxight® sequences over 18 genes and more than 60 alleles to identify how patients are likely to react to over 200 different medications, including Xeljanz.


Knowing which polymorphisms a patient holds may reduce the probability of that patient suffering from adverse reactions to the medications they are taking. If the patient doesn’t respond to the medication appropriately, a more suitable drug will be offered.


To find out more about Rxight,® contact us at 1-888-888-1932 or support@Rxight.com.


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