Xeljanz (tofacitinib citrate) is a Janus kinase (JAK) inhibitor used in the treatment of rheumatoid arthritis, psoriatic arthritis, polyarticular course juvenile idiopathic arthritis, ankylosing spondylitis and ulcerative colitis. It is a disease-modifying anti-rheumatic drug (DMARD) and a small molecule drug, rather than a biological agent.

Weight gain and weight loss were not identified as side effects during clinical development of Xeljanz.

Why is weight loss while taking Xeljanz a concern?

While not a direct side effect of Xeljanz, it’s important to keep an eye on unexplained weight loss while taking the drug. Xeljanz affects the immune system and lowers your ability to fight off serious infections, such as tuberculosis (TB). TB can cause weight loss, as well as other symptoms of an infection.

Weight loss can also be a symptom of ulcerative colitis.

Does body weight affect the dose of Xeljanz?

Children taking Xeljanz for polyarticular course juvenile idiopathic arthritis will need their dosage adjusted if they weigh less than 40kg. Xeljanz 5mg twice a day is recommended for those weighing 40kg or more, which can be given in the form of a tablet or oral solution.

A 4ml (4mg) dose of the Xeljanz oral solution given twice daily is recommended for patients weighing ≥20kg and ﹤40kg, while a 3.2ml dose given twice a day is recommended for patients weighing ≥10kg and ﹤20kg.

A tablet, extended-release tablet and oral solution formulations of Xeljanz have been approved by the US Food and Drug Administration (FDA).