Baricitinib

Key facts

• Baricitinib (sold as Olumiant) is a JAK inhibitor: it blocks signaling proteins (Janus kinases) that immune cells use to drive inflammation.
• It's taken as a tablet once daily, and effects on joint pain or skin symptoms typically build over several weeks.
• Baricitinib carries a recognized class-wide warning: serious infections, blood clots, major cardiovascular events such as heart attack or stroke, and certain cancers occur more often with JAK inhibitors than with some older treatments, and the risk rises with age and existing cardiovascular risk factors.
• Seek urgent care for chest pain, sudden shortness of breath, one-sided leg swelling, or signs of a serious infection such as high fever.

What baricitinib treats

Baricitinib treats rheumatoid arthritis and moderate-to-severe atopic dermatitis (eczema) that hasn't responded well enough to other treatments. It's also used for certain other inflammatory conditions, including alopecia areata, under specialist supervision.

How baricitinib works

Immune cells use enzymes called Janus kinases (JAKs) to relay signals from outside the cell to the nucleus, switching on genes that drive inflammation. Baricitinib blocks these enzymes, interrupting that signal and reducing the inflammation that causes joint pain, swelling, and skin symptoms.

Before you take it

• Tell your doctor about any current or recent infection, including tuberculosis, shingles, or hepatitis, since baricitinib can allow infections to worsen or reactivate.
• Tell your doctor about a history of blood clots, heart attack, stroke, or smoking; baricitinib is linked to higher rates of blood clots and major cardiovascular events, particularly over 65 or with existing cardiovascular risk factors.
• Tell your doctor about any history of cancer, since JAK inhibitors carry a higher reported rate of certain cancers, including lymphoma and skin cancer, with long-term use.
• Avoid live vaccines while on baricitinib unless your doctor confirms it's safe.
• Baricitinib should not be used in pregnancy; discuss contraception with your doctor.

Side effects

Common effects include upper-respiratory infections, nausea, headache, and changes in cholesterol levels seen on blood tests.

Stop and seek urgent medical care for any of these:

• Fever, chills, or other signs of serious infection.
• Chest pain, sudden shortness of breath, or leg swelling (possible blood clot or heart problem).
• Sudden weakness, numbness, or difficulty speaking (possible stroke).
• Unusual bruising, bleeding, or persistent fatigue.

Safety essentials

• Baricitinib's defining risks, as a JAK inhibitor, are serious infections, blood clots, major cardiovascular events, and certain cancers. This combined warning applies to the whole drug class, which is why ongoing monitoring, not just symptom awareness, is part of treatment.
• Regular blood tests check cholesterol, liver function, and blood counts throughout treatment.
• Report any new infection, unusual swelling, or chest symptoms promptly rather than waiting for your next scheduled review.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.