Tofacitinib, is a type of drug known as a Janus kinase (JAK) inhibitor. It works by blocking the action of Janus kinase enzymes, which are involved in the inflammation that causes the symptoms of rheumatoid arthritis and psoriatic arthritis.

It helps to decrease pain/tenderness/swelling in the joints. Tofacitinib is also used to treat a certain bowel disease (ulcerative colitis).