An oral JAK inhibitor for rheumatoid arthritis and eczema
Baricitinib
An oral tablet used for rheumatoid arthritis, eczema and severe hair loss that works by calming an overactive immune response.
What is Baricitinib?
Baricitinib is a specialist tablet used for rheumatoid arthritis, moderate to severe atopic eczema and severe hair loss (alopecia areata) when other treatments have not controlled them well enough. It is a JAK inhibitor, which dampens the overactive immune signals that drive these conditions. It is taken by mouth once a day. Like other JAK inhibitors, it carries important warnings about serious infections, including shingles and tuberculosis, blood clots, major heart and circulation problems and certain cancers, especially in older people and smokers, so people are screened and monitored and their vaccinations are checked beforehand.
Education and reference only. This is a plain-language guide to Baricitinib — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Baricitinib is a medicine called a JAK inhibitor, used to treat several conditions driven by an overactive immune system: rheumatoid arthritis, moderate to severe atopic eczema, and severe alopecia areata, a condition causing patchy or extensive hair loss. It is used when other treatments have not worked well enough. It is taken by mouth as a once-daily tablet and is started and supervised by specialist teams who screen for infections and other risks before treatment begins.
How it works
Many immune conditions are driven by chemical messengers that travel into cells and switch on inflammation through a pathway called JAK. Baricitinib blocks part of this pathway, so fewer of these inflammatory signals get through. In rheumatoid arthritis this eases joint inflammation and pain; in eczema it calms the skin; and in alopecia areata it can allow hair to regrow. Because the same JAK pathway helps the immune system fight infection, dampening it explains both the benefit and the main safety risks of the medicine.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist oral medicine used in the UK for rheumatoid arthritis, moderate to severe eczema, and severe hair loss (alopecia areata) when other treatments have not worked well enough.
What it treats
Conditions Baricitinib is used for
Practical use
How to take Baricitinib
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it by mouth once a day, at about the same time each day, with or without food.
- Swallow the tablet whole with water rather than crushing or splitting it.
- Keep up with the blood tests and reviews your specialist arranges, as these check the medicine is safe for you.
- Tell your team promptly about any signs of infection, such as fever, a persistent cough or a painful blistering rash.
- Do not have live vaccines without checking first, and tell any health professional that you take a JAK inhibitor.
Weighing it up
Advantages & disadvantages of Baricitinib
Advantages
- Helps several immune conditions, including rheumatoid arthritis, eczema and severe hair loss, when other treatments have not worked.
- Taken as a once-daily tablet rather than an injection.
- Can ease joint pain and inflammation or improve skin and hair, depending on the condition.
Disadvantages
- Carries class warnings about serious infections, blood clots, heart problems and certain cancers, especially in older people and smokers.
- Needs screening before starting and regular blood tests during treatment.
- Live vaccines are generally avoided, and it is only started under specialist care.
Practical use
Good to know
The most important thing to understand about baricitinib is that, like other JAK inhibitors, it carries serious safety warnings. Because it dampens the immune system, it can make serious infections more likely, including shingles and tuberculosis, so people are screened and their vaccinations checked before starting and watched for infection during treatment. There is also a recognised risk of blood clots in the legs or lungs, major heart and circulation problems and certain cancers, which is greatest in people over a certain age, smokers or former smokers, and those with heart or cancer risk factors; in these groups it is only used when no suitable alternative exists. It is a long-term treatment that needs regular blood tests and review. Live vaccines are generally avoided while taking it.
Who should not take it / use with caution
- People who have had a serious allergic reaction to baricitinib should not take it.
- It is generally avoided in people with a serious active infection, including tuberculosis, until this is treated.
- It is used with great caution, or avoided, in people at higher risk of blood clots, heart problems or cancer, such as older people and smokers.
- It is not recommended in pregnancy, and effective contraception is advised; discuss family planning with your specialist.
Monitoring
- Screening for infections such as tuberculosis and hepatitis, and checking vaccinations, before starting.
- Regular blood tests to check blood counts, cholesterol and liver and kidney function.
- Watching for signs of infection, blood clots, heart problems and skin changes throughout treatment.
Side effects
- Cold-like symptoms, sore throat or headache.
- A higher chance of infections, including shingles and chest or urinary infections.
- Raised cholesterol or changes in liver blood tests.
- Less commonly but seriously, blood clots, major heart or circulation events, or certain cancers, which is why screening and monitoring are used.
Key interactions
- It can interact with some other medicines that affect how it is handled by the body, so give your team a full medicines list.
- Taking it with other medicines that weaken the immune system increases the risk of infection.
- Live vaccines are generally avoided while on treatment.
Available as: Tablets taken by mouth.
Answers
Baricitinib: frequently asked questions
What is baricitinib used for?
It is used for rheumatoid arthritis, moderate to severe atopic eczema and severe hair loss (alopecia areata) when other treatments have not controlled them well enough.
How does it work?
It is a JAK inhibitor that blocks part of the immune signalling system in cells, calming the overactive response that drives joint, skin and hair conditions.
What are the main safety concerns?
Like other JAK inhibitors, it can raise the risk of serious infections, blood clots, heart and circulation problems and certain cancers, especially in older people and smokers, so people are screened and monitored.
Will I need blood tests?
Yes. You will have blood tests before starting and regularly during treatment to check your blood counts, cholesterol and liver and kidney function.
Can I have my usual vaccinations?
Live vaccines are generally avoided while taking it, so always check with your specialist team before having any vaccine.
The wider class
About JAK inhibitor (oral)
Baricitinib belongs to the jak inhibitor (oral) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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