What is baricitinib?

Baricitinib (Olumiant™) is a type of drug known as a JAK inhibitor. These drugs work by interfering with the inflammatory processes within the immune system that lead to the symptoms of rheumatoid arthritis.

Baricitinib is a long-term treatment. Most people who benefit from this treatment will notice an improvement within four weeks of starting treatment but further improvements may be seen over the first six months of treatment. It can be used alone or with methotrexate.

Baricitinib is taken as tablets and can be prescribed by a consultant rheumatologist for adults with rheumatoid arthritis.

Are there any reasons I won't be prescribed baricitinib?

Baricitinib won’t be started if:

  • your arthritis isn’t active
  • you haven’t tried other treatments appropriate for your condition first
  • you’re pregnant or planning to try for a baby.

Your doctor may decide not to prescribe this treatment if you have or have had any of the following:

  • an infection
  • shingles
  • lung disease
  • hepatitis or other liver problems, or kidney disease
  • heart problems, high blood pressure or high cholesterol, or blood clots (deep vein thrombosis or pulmonary embolism)
  • stomach ulcers

You’ll probably have blood tests before treatment starts to assess your disease and whether the drug is suitable for you. Your doctor will need to check if you’ve previously been exposed to tuberculosis (TB) or hepatitis. If you’ve been exposed to TB you may need a course of treatment for latent (asymptomatic) TB before starting baricitinib.

If you’ve previously had hepatitis you may need regular checks for this as baricitinib may increase the risk of the hepatitis being reactivated.

If you’re taking other drugs alongside your baricitinib (such as methotrexate) you’ll also need to continue your blood tests for these.

Your rheumatology team will also monitor your immune system once you start treatment. If your red or white blood cell count gets too low, your treatment may be stopped until it improves.

You may have to be monitored for other conditions as well, for example if you have liver problems or high cholesterol. Baricitinib raises cholesterol levels in some people.

How is it taken?

Baricitinib is taken as a 4 mg tablet once a day. In some circumstances a 2 mg tablet may be prescribed instead.

If you take more than the recommended dose by mistake, contact your doctor immediately. If you miss a dose, carry on with the usual dose the next day – do not double it.

If you haven’t noticed any improvement in your symptoms after six months, discuss it with your doctor, who may decide to stop the baricitinib treatment.

Because it’s a long-term treatment, it’s important to keep taking baricitinib (unless you have severe side-effects):

  • even if it doesn’t seem to be working at first
  • even when your symptoms improve (to help keep the disease under control).

Side-effects and risks

Like any medicine, baricitinib can cause side-effects. Baricitinib and the other JAK inhibitors are a fairly new group of medicines. Because of this, we know less about the risk of longer-term side effects than we do for other medicines used for rheumatoid arthritis. Your rheumatology team should keep you up to date if any new information becomes available about side-effects.

Because baricitinib affects your immune system, it can make you more likely to pick up infections. These include throat, nose and chest infections, cold sores, skin infections (cellulitis) and urinary tract infections. There seems to be a particular risk of shingles (a skin infection caused by the chicken pox virus) in people who take JAK inhibitors.

Tell your doctor or rheumatology nurse straight away if you develop any signs of infection such as a sore throat or fever, or any other new symptoms that concern you. Other symptoms of infection may include fever and chills, persistent cough or headaches, unusual tiredness, or dental problems. If any of these symptoms are severe, you should stop taking baricitinib and see your doctor straight away.

You should see your doctor if you develop chickenpox or shingles or come into contact with someone who has chickenpox or shingles. These can be severe if you’re on baricitinib. You may need antiviral treatment, and you may need to stop taking baricitinib until you’re better.

Some people who take baricitinib develop reductions in white blood cells, raised liver blood tests and raised levels of cholesterol in the blood. These problems are usually mild but your rheumatology team will arrange regular blood checks while you’re taking baricitinib as a precaution.

Nausea (sickness) is fairly common when taking baricitinib but may settle with time. If you develop nausea you should discuss this with your rheumatology team.

It’s possible that baricitinib may increase the risk of blood clots (deep vein thrombosis and pulmonary embolism). The risk is likely to be greater if you’ve had either of these before. You should seek urgent medical care if you develop swelling of the legs or breathlessness.

It’s uncertain whether there may also be a slightly increased risk of some cancers in people taking baricitinib – research so far hasn’t convincingly confirmed this risk, but if you’ve had previous cancers, this may influence the decision to offer baricitinib as a treatment.

Reducing the risk of infection

Try to avoid close contact with people with severe active infections.

For advice on avoiding infection from food, visit NHS Choices - 10 ways to stop food poisoning.

Effects on other treatment

You’ll probably be taking methotrexate as well as baricitinib. Check with your doctor before starting any new medicines, and remember to mention you’re on baricitinib if you’re treated by anyone other than your usual rheumatology team.


It’s best to discuss any vaccinations you might need with your doctor before starting baricitinib. It’s generally recommended that people on baricitinib avoid live vaccines such as yellow fever.

If you’re offered shingles vaccination (Zostavax) it’s best if you can have this before starting baricitinib. Shingles vaccination isn’t recommended for people who are already on baricitinib.

Pneumovax (which protects against the most common cause of pneumonia) and yearly flu vaccines are safe and recommended.

Having an operation

If you’re thinking about having surgery, talk this over with your specialists. It’s likely you will be advised to stop baricitinib for a time before and after surgery.


There’s no known interaction between baricitinib and alcohol, However, if you’re also taking methotrexate, you should keep well within the recommended limits of no more than 14 units of alcohol per week for adults because methotrexate and alcohol can interact and affect your liver. In some circumstances your doctor may advise lower limits.

Fertility, pregnancy and breastfeeding

As we know very little about the effects of baricitinib in pregnancy, it’s important not to get pregnant while taking this treatment. If you’re planning to try for a baby or you’re already pregnant, your doctor will not prescribe it. Women who could become pregnant should use effective contraception while being treated with baricitinib and for at least a week after stopping the treatment.

It is not known whether baricitinib passes into human breastmilk so you should talk to your rheumatology team if you’re thinking of breastfeeding.

There’s no information currently available about whether baricitinib might affect male or female fertility.