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JAK inhibitors

JAK inhibitors are the newest class of drugs used to treat RA. Like biologic drugs, these are ‘targeted’ therapies, which work on the immune response. Unlike the biologics, they can be taken in tablet form.

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JAK inhibitor name	Brand name	Method of administration
Tofacitinib	Xeljanz	Tablets
Baricitinib	Olumiant	Tablets

Most commonly reported side effects

As with any medication, the JAK inhibitors have a number of possible side effects, although it is important to remember that these are only potential side effects. They may not occur at all.

Common side effects may include:

• infections of nose, throat or the windpipe
• lung infection (pneumonia and bronchitis)
• shingles
• influenza
• urinary bladder infection (cystitis)
• increased liver enzymes or muscle enzymes in the blood (signs of liver or muscle problems)
• high levels of blood fat (cholesterol) shown by a blood test

More information on side effects can be found in the patient information leaflet for tocilizumab. Remember to report any concerns about possible side effects to the doctors and nurses.

JAK inhibitors with other medicines

Tofacitinib

Tofacitinib can interact poorly with the following medications:

• antibiotics such as clarithromycin and rifampicin used to treat bacterial infections
• fluconazole, ketoconazole, clotrimazole, itraconazole, and voriconazole, used to treat fungal infections

Baricitinib

Baricitinib can interact poorly with the following medications:

• probenecid (for gout), since this medicine may increase the levels of baricitinib in your blood. If you are taking probenecid, the recommended dose of baricitinib is 2 mg once a day
• injectable anti-rheumatic medicine
• medicines which are used to control the body’s immune response, such as azathioprine, tacrolimus or ciclosporin
• other medicines belonging to the group of Janus kinase inhibitors, such as ruxolitinib

JAK inhibitors during pregnancy and breastfeeding

Tofacitinib

The manufacturers recommend that tofacitinib should not be administered to pregnant women and that a gap of at least 4 weeks should be left from the last dose of the drug and trying to conceive. Tofacitinib is not recommended to be taken while breastfeeding.

Baricitinib

The manufacturers recommend that baricitinib should not be administered to pregnant women and that a gap of at least 1 week should be left from the last dose of the drug and trying to conceive, as it is not known whether the drug can pass into the milk. Baricitinib is not recommended to be taken while breastfeeding, as it is not known whether the drug can pass into the milk.

JAK inhibitors and alcohol

 The manufacturers of both tofacitinib and baricitinib have not issued any guidance to limit alcohol intake while taking these drugs. However, it is not uncommon for people taking JAK inhibitors to be on other medications as well, where different guidance applies. Methotrexate, for example, can affect the liver, so for those taking methotrexate alongside their biologic, moderate intake of alcohol is recommended in line with government guidelines.

JAK inhibitors and immunisations/ vaccinations

It is recommended that before starting tofacitinib or baricitinib, patients should be up-to-date with their vaccinations, and that live vaccines should be avoided while on the drug. For baricitinib, it is recommended that any necessary live vaccines be given at least 2, but preferably 4 weeks prior to starting it. The manufacturers of both drugs suggest that the exact time period for this should be in accordance with current vaccination guidelines, and your rheumatology team can advise you.

Medicines in rheumatoid arthritis

We believe it is essential that people living with RA understand why certain medicines are used, when they are used and how they work to manage the condition.

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