Baricitinib !
An oral JAK1/JAK2 inhibitor for rheumatoid arthritis after a TNF blocker, alopecia areata and severe COVID-19 in hospital.
Updated 2026-11-01
The figure shows the human JAK2 kinase domain with baricitinib in its ATP site.
Mechanism of action
Baricitinib is a reversible ATP-competitive inhibitor of JAK1 and JAK2. It reduces signalling of cytokines such as IL-6 and the interferons, which lowers STAT activation, lymphocyte activity and inflammation; in severe COVID-19 it damps the excessive inflammatory response.
- Binds the ATP site of JAK1 and JAK2
- STATs are not phosphorylated
- Less cytokine-driven inflammation
Pharmacokinetics
- Absorption
- Oral, once daily
- Elimination
- Kidney disease is taken into account before and during treatment
Indications
- Rheumatoid arthritis after one or more TNF inhibitors Rheumatoid arthritis →
- Alopecia areata Alopecia areata →
- COVID-19 in hospitalised adults who need oxygen, ventilation or ECMO COVID-19 →
Adverse effects
Common
- Upper respiratory infections
- Nausea
- Raised cholesterol
- Herpes zoster
Contraindications
- Active serious infection, including active tuberculosis
- Hypersensitivity to baricitinib
Key interactions
- Other immunosuppressants and biologic DMARDs
- Added immunosuppression and infection risk.
- Live vaccines
- Avoided during treatment.
What is monitored
- Latent TB test before and during treatment
- Blood count, liver tests, kidney function and cholesterol
- Signs of thrombosis and new abdominal pain
Administration and safety
- Oral tablet, with or without food, at about the same time each day.
Nursing care
- Before starting, confirm the latent TB test, hepatitis screening, blood count and up-to-date vaccines.
- Ask about smoking, previous heart attack, stroke or blood clots.
- Teach the signs of a clot (painful swollen leg, sudden shortness of breath, chest pain) and of shingles (painful band-shaped rash).
- Live vaccines are avoided during treatment.
- Ask about kidney disease, ulcers or diverticulitis; breastfeeding is avoided during treatment and for a short time after.
Pregnancy and breastfeeding
Human data are limited; the treating team weighs benefits and risks.
Test yourself
Think of the answer, then tap the question to see it.
Which Janus kinases does baricitinib inhibit?
JAK1 and JAK2.
Which hair-loss disease is an indication for baricitinib?
Alopecia areata.
Which serious cardiovascular risks share a warning with baricitinib and tofacitinib?
Heart attack, stroke and blood clots in the legs, lungs or arteries.
Related drugs
Related conditions
← Back to the class: JAK inhibitors
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Baricitinib: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2022); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 39 (McGraw Hill, 2023); Altered Immunocompetence | Vaccines & Immunizations | CDC (Centers for Disease Control and Prevention (CDC), 2024); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.