JAK inhibitors and targeted synthetic DMARDs

01Purpose and principlesWhat the treatment does and how it fits into care.

Targeted synthetic DMARDs are chemically manufactured oral medicines aimed at defined intracellular pathways. Tofacitinib inhibits JAK1 and JAK3 with functional JAK2 effects, baricitinib mainly JAK1 and JAK2, and upadacitinib is JAK1-selective at therapeutic exposure. By interrupting signalling from multiple cytokine receptors, they can improve synovitis rapidly but also impair antiviral, mycobacterial and haematopoietic defence.

The major safety change is class-level risk stratification. In the ORAL Surveillance study, tofacitinib produced more major cardiovascular events and malignancy than TNF inhibition in rheumatoid patients aged 50 or older with cardiovascular risk. MHRA extended precautions to all JAK inhibitors used for chronic inflammatory disorders. For people aged 65 or over, current or former long-term smokers, or those with cardiovascular or cancer risk, use a JAK inhibitor only when no suitable alternative exists. Use caution with VTE risks and the lower authorised dose when available.

This is a comparative decision, not a tick-box contraindication. Document age, smoking pack-years and cessation, previous MI, stroke, peripheral vascular disease, hypertension, diabetes, lipids, obesity, immobility, previous VTE or thrombophilia, oestrogen exposure, cancer history and skin-cancer risk. Explain that infection, zoster, thrombosis, MACE and malignancy risks are considered together against the harm of uncontrolled disease and alternative biologic options.

Pre-treatment testing mirrors biologic safety but adds laboratory and vascular baselines. Exclude active serious infection, test IGRA and chest risk for TB, obtain HBsAg, anti-HBc and anti-HBs, HCV and HIV tests, and review varicella or zoster. Check FBC with differential, ALT or AST, creatinine and eGFR and fasting lipids. Update inactivated vaccines and use recombinant zoster vaccine where eligible; give any required live vaccine before immunosuppression.

During treatment, serious bacterial infection, opportunistic infection, TB and herpes zoster require interruption. Localised uncomplicated zoster may be treated promptly with an individual hold, whereas disseminated or ophthalmic disease needs admission and IV antiviral assessment. An unexplained fall in haemoglobin, neutrophils or lymphocytes follows the product interruption table rather than routine reassurance.

VTE prevention is not achieved by routine anticoagulation for everyone. Avoid or reconsider JAK therapy when previous VTE, major surgery, immobilisation, active cancer, inherited thrombophilia or combined risk makes another effective drug safer. Educate every patient about unilateral swelling, sudden dyspnoea and pleuritic pain. Temporarily withhold around major surgery through the perioperative plan and restore mobility and standard thromboprophylaxis.

Apremilast inhibits phosphodiesterase 4 and is licensed for psoriatic arthritis and psoriasis. Titrate over five days to 30 mg orally twice daily; in severe renal impairment reduce to 30 mg once daily using the product titration schedule. It does not require the same TB or blood monitoring as a JAK inhibitor, but early diarrhoea, nausea, weight loss, insomnia and depression or suicidal thinking require active review.

Neither JAK inhibitors nor apremilast should be used during pregnancy or breastfeeding. Tofacitinib requires effective contraception during treatment and for four weeks after the last dose. Other JAK products have their own intervals, so document the brand rather than applying one generic washout. Establish control on hydroxychloroquine, sulfasalazine, azathioprine, TNF inhibition or another proven compatible option before conception.

Assess efficacy against the commissioned disease target within the required interval. If a JAK inhibitor fails, distinguish inadequate exposure, non-inflammatory pain, infection and true mechanism failure. Do not combine it with a biologic. Switch to an alternative mechanism with a deliberate interruption interval that limits both flare and overlapping immune suppression.

Key points

JAK inhibitors are oral small molecules that block intracellular cytokine signalling; faster onset and oral convenience do not make them lower-risk than injectable biologics.
MHRA requires all JAK inhibitors for chronic inflammatory disorders to be used only when no suitable alternatives exist in people aged 65 or over, current or past long-term smokers, and those with cardiovascular or malignancy risk.
Use caution in anyone with venous-thromboembolism risk and use the lower authorised dose where the product recommends it for risk reduction.
Before treatment, screen active and latent tuberculosis, hepatitis B and C and HIV, review vaccines and zoster history, and obtain FBC, liver and renal profiles plus fasting lipids.
Tofacitinib for adult rheumatoid or psoriatic arthritis is 5 mg orally twice daily; the 10 mg twice-daily dose is not a rheumatoid-arthritis regimen and carries greater thrombotic risk.
Do not combine a JAK inhibitor with a biologic DMARD or another potent immunosuppressant such as ciclosporin because additive infection and immune suppression outweigh evidence of benefit.
Check lipids about eight weeks after starting and monitor counts, liver and renal function at the product-specific interval; cytopenia thresholds determine interruption.
Herpes zoster is a prominent class toxicity. Give recombinant zoster vaccine before treatment where eligible and investigate painful dermatomal or disseminated lesions promptly.
Apremilast is a PDE4 inhibitor rather than a JAK inhibitor and has less laboratory immunosuppression, but diarrhoea, weight loss, depression and severe renal impairment modify its use.
JAK inhibitors and apremilast are not compatible with pregnancy or breastfeeding; apply each product's contraception interval and switch to a proven compatible DMARD before conception.

02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.

Rapid anti-inflammatory response

JAK inhibition can reduce synovitis and stiffness within weeks, but continuation still requires the disease-specific NICE response threshold and acceptable safety.

Herpes zosterRed flag

Pain, dysaesthesia and grouped vesicles can be subtle; ophthalmic distribution, dissemination, neurological features or immunocompromised systemic illness is urgent.

Venous thromboembolismRed flag

Unilateral swelling or pain, sudden breathlessness, pleurisy, haemoptysis or unexplained tachycardia requires immediate DVT or pulmonary-embolism assessment.

Major cardiovascular eventRed flag

Central chest pressure, autonomic symptoms, focal weakness, dysphasia or acute visual loss requires emergency coronary or stroke care and drug interruption.

Laboratory toxicity

Falling lymphocytes, neutrophils or haemoglobin, rising transaminases or renal decline changes safe exposure and may cross product-specific interruption thresholds.

Apremilast intoleranceRed flag

Early persistent diarrhoea, nausea, significant weight loss, insomnia, depression or suicidal thinking requires dose, hydration and continuation review.

Red flags requiring action

Fever, hypotension, confusion, hypoxaemia, widespread vesicles or focal severe infection requires immediate JAK-inhibitor withholding and urgent antimicrobial assessment.
New unilateral leg swelling, pleuritic pain, haemoptysis, unexplained tachycardia or sudden dyspnoea requires emergency venous-thromboembolism assessment.
Chest pressure, diaphoresis, focal neurological loss, speech change or acute limb ischaemia requires the relevant myocardial-infarction or stroke pathway.
Severe abdominal pain, guarding or fever can indicate diverticulitis or gastrointestinal perforation and should not be treated as routine drug-related diarrhoea.
New lymphadenopathy, weight loss, persistent cough, skin lesion or unexplained anaemia requires malignancy and infection assessment rather than automatic continuation.
Pregnancy on a JAK inhibitor or apremilast requires immediate specialist review because these medicines are not compatible with pregnancy or breastfeeding.

03Assessment before treatmentTests and checks that guide safe selection.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
First-line vascular and cancer risk inventoryFirst stepFirst line
Why
Determine whether MHRA requires use only after suitable alternatives and whether VTE risk is acceptable.
Interpretation and limitations
Document age, smoking, prior MACE or VTE, vascular and metabolic factors, malignancy, immobility, surgery and oestrogen exposure; reassess these risks over time.
02
TB, hepatitis, HIV and vaccine assessment
Why
Prevent reactivation and severe vaccine-preventable infection before JAK blockade.
Interpretation and limitations
Combine IGRA with exposure and chest history, use HBsAg plus anti-HBc and anti-HBs, obtain HCV and HIV testing and complete required vaccines before treatment when possible.
03
Baseline FBC with differential
Why
Confirm lymphocyte, neutrophil and haemoglobin values meet product initiation criteria.
Interpretation and limitations
Do not start below the agent-specific threshold; investigate unexplained cytopenia and use the product interruption table rather than a universal DMARD cutoff.
04
Liver, renal and interaction review
Why
Select the correct dose and avoid excessive exposure.
Interpretation and limitations
eGFR and hepatic category alter tofacitinib, baricitinib or apremilast dosing; strong CYP3A4 inhibitors or inducers materially change tofacitinib exposure.
05
Fasting lipid profile
Why
Create a cardiovascular baseline and quantify treatment-emergent lipid change.
Interpretation and limitations
Repeat about eight weeks after tofacitinib, then manage cholesterol and the global vascular risk; an increase also reopens whether a TNF or other alternative is safer.
06
Disease-specific activity measure
Why
Confirm eligibility and objectively test whether targeted therapy is worth continuing.
Interpretation and limitations
Use the score and assessment window specified by the rheumatoid, psoriatic or axial NICE pathway; normal CRP alone does not establish remission.
07
Symptom-directed infection or thrombosis tests
Why
Investigate high-consequence adverse events without waiting for routine monitoring.
Interpretation and limitations
Culture and image suspected infection; use compression ultrasound, D-dimer only within a validated probability pathway, or CT pulmonary angiography for VTE as clinically indicated.

04Treatment approachPreparation, options, escalation and aftercare.

01First selection gateCompare JAK risk with suitable alternativesFirst stepA targeted synthetic DMARD is being considered after the disease-specific prior-treatment sequence.

1Confirm active inflammatory disease and NICE eligibility, then document age, smoking, cardiovascular, malignancy, VTE, infection and reproductive risk.
2AlternativeIn MHRA high-risk groups, use a JAK inhibitor only if no suitable alternative can meet the same clinical need and record why.
3Select the exact product and authorised lower dose where relevant, with an efficacy target and stop criteria agreed before initiation.

02Pre-treatment and dosingScreen infection and use the product tableThe risk-benefit decision favours a named JAK inhibitor or apremilast.

1Complete TB, hepatitis, HIV, vaccine, blood-count, liver, renal, lipid and pregnancy assessment appropriate to that product.
2Prescribe the licensed indication-specific dose and adjust for eGFR, hepatic function, age or interactions; do not infer doses across molecules.
3Provide written red flags for infection, zoster, VTE, MACE, abdominal emergency and mood change, and identify who can advise withholding.

03Toxicity responseStop and investigate the syndromeSerious infection, zoster, thrombosis, cardiovascular event, cytopenia or possible perforation develops.

1Withhold the targeted drug immediately and use the relevant emergency pathway for sepsis, antiviral therapy, VTE, ACS, stroke or acute abdomen.
2Review all new provoking factors, laboratory thresholds, dose and interactions, and report or document serious suspected adverse reactions.
3Restart only after recovery and a specialist reassessment; a new vascular or malignancy event may make another mechanism permanently preferable.

04Apremilast routeTitrate and watch weight and moodPreferredPsoriatic disease meets an apremilast pathway and a less immunosuppressive oral option is preferred.

1Use the five-day starter titration to 30 mg twice daily, reducing maintenance to 30 mg once daily in severe renal impairment.
2Record weight, gastrointestinal tolerance, sleep and depression or suicidal history and provide early contact for severe diarrhoea or mood change.
3Assess joint and skin response at the NICE continuation interval and stop when the required improvement is not reached.

05Preconception switchWithdraw incompatible targeted therapyPregnancy is planned or occurs during a JAK inhibitor or apremilast course.

1Stop the incompatible medicine, use its exact post-treatment contraception interval and involve rheumatology and maternity promptly after exposure.
2Establish disease control on a pregnancy-compatible conventional or biologic DMARD before attempting conception whenever possible.
3AlternativeDo not use the medicine during breastfeeding; select an alternative with established lactation compatibility.

05Regimens, contraindications and interactionsTreatment details and the circumstances that modify them.

Oral JAK inhibitor for eligible inflammatory arthritis after disease-specific prior therapy and explicit MHRA risk stratification.

Tofacitinib

Give 5 mg orally twice daily for adult rheumatoid or psoriatic arthritis; reduce to 5 mg once daily in specified moderate or severe renal impairment, moderate hepatic impairment or potent interaction settings under the product table.

Do not use 10 mg twice daily for rheumatoid arthritis. Avoid serious infection, combine with neither biologic nor potent immunosuppressant, and review MACE, VTE, cancer, zoster, cytopenia and pregnancy.

JAK1 and JAK2 inhibitor for eligible rheumatoid arthritis where alternatives and class risks have been weighed.

Baricitinib

Give 4 mg orally once daily for adult rheumatoid arthritis; use 2 mg once daily in adults aged 65 or over and when product-defined infection, VTE, MACE, malignancy or renal factors favour the lower authorised dose.

Check renal function and blood counts, avoid active TB or serious infection and review thrombosis, cardiovascular and malignancy risk; do not use during pregnancy or breastfeeding.

Selective JAK1 inhibitor for eligible peripheral or axial inflammatory disease after the required previous treatment.

Upadacitinib

Give 15 mg orally once daily for adult rheumatoid arthritis, psoriatic arthritis or axial spondyloarthritis; swallow the prolonged-release tablet whole and follow indication-specific interaction and renal guidance.

Review serious infection, zoster, TB, hepatitis, cytopenia, lipids, VTE, MACE, malignancy, gastrointestinal perforation and reproductive contraindications.

PDE4 inhibitor for eligible active psoriatic arthritis or psoriasis; it is targeted synthetic therapy but not a JAK inhibitor.

Apremilast

Use the five-day starter titration, then give 30 mg orally twice daily approximately twelve hours apart; in severe renal impairment use 30 mg once daily after the adjusted titration.

Monitor diarrhoea, nausea, dehydration, weight, insomnia, depression and suicidal thinking; strong CYP3A4 inducers reduce effect, and pregnancy or breastfeeding is not compatible.

Non-live prevention against herpes zoster, a particularly relevant infection during JAK blockade.

Recombinant zoster vaccine

Give the current UK age- and risk-appropriate two-dose schedule before or during therapy where eligible, preferably completing vaccination before JAK inhibition when disease urgency allows.

Confirm current Green Book eligibility and interval; vaccination reduces but does not abolish zoster, and active shingles is treated before immunosuppression resumes.

06Complications, monitoring and follow-upAdverse effects, response and longer-term review.

Repeat FBC, liver and renal profiles at the product and shared-care intervals, with earlier testing after dose change, infection, renal decline or interacting medicine; apply molecule-specific interruption thresholds.
Repeat fasting lipids around eight weeks after tofacitinib or as directed for the chosen JAK inhibitor, then treat overall cardiovascular risk and reconsider class suitability when risk changes.
Ask at every review about infection, shingles, TB symptoms, unilateral leg swelling, chest or neurological symptoms, abdominal pain, malignancy warning signs and new smoking or immobility exposure.
Measure the commissioned disease response within the NICE assessment window and stop an ineffective medicine rather than retaining its vascular and infectious risk for oral convenience.
For apremilast, record weight and gastrointestinal and psychiatric tolerance early, with more frequent review in underweight patients or those with depression.
Revisit contraception, pregnancy intention and vaccine status at each transition, surgery or change in risk; update the written hold and restart instructions.

07Special situationsVariants, exceptions and circumstances that change the usual approach.

Oral route does not mean conventional risk

JAK inhibitors can suppress multiple cytokine networks and carry infection and vascular risks comparable to or greater than selected biologics.

Risk restriction is comparative

MHRA does not make age 65 an absolute ban, but requires evidence that no suitable alternative offers a better balance.

A lipid rise changes global risk

Treating cholesterol may be appropriate, yet the new profile still belongs in the documented JAK-versus-TNF decision.

Zoster can precede rash

Dermatomal pain or dysaesthesia may appear before vesicles, allowing early antiviral assessment in an immunosuppressed patient.

Dose tables are molecule-specific

Renal impairment, CYP interactions and risk-reduction doses differ among tofacitinib, baricitinib, upadacitinib and apremilast.

Apremilast is mechanistically separate

Its PDE4 action and monitoring profile differ from JAK blockade, so class warnings should not be copied indiscriminately.

08Common pitfallsFrequent interpretation and management errors.

01
Choosing a JAK inhibitor for oral convenience without documenting smoking, vascular, VTE, malignancy and suitable-alternative assessment.
02
Prescribing tofacitinib 10 mg twice daily for rheumatoid arthritis by borrowing a dose from a different indication.
03
Combining a JAK inhibitor with a biologic during a switch because one medicine has not yet worked.
04
Treating unilateral leg swelling or pleuritic pain as a routine flare in a patient with JAK and immobilisation risks.
05
Using one renal-adjustment rule for every targeted synthetic molecule instead of the named product information.
06
Applying JAK laboratory assumptions to apremilast while missing weight loss, diarrhoea and psychiatric toxicity.