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JAK inhibitor (JAK1/JAK2) — systemic immunosuppressant Pregnancy: CONTRAINDICATED — teratogenic in animal studies. Effective contraception required during treatment and for at least 1 week after stopping.

Baricitinib 2–4mg (Atopic Dermatitis / Alopecia Areata)

Brand names: Olumiant (2 mg and 4 mg tablets)

Adult dose

Dose: Atopic dermatitis: 4 mg once daily (reduce to 2 mg once daily after adequate control). Severe alopecia areata: 4 mg once daily.
Route: Oral
Frequency: Once daily
Max: 4 mg/day
Atopic eczema: start 4 mg OD; after adequate clinical response (usually 12–16 weeks), step down to 2 mg OD maintenance. Use with topical corticosteroids as needed. Alopecia areata: 4 mg OD — BRAVE-AA trials. Discontinue if no response after 16 weeks (eczema) or 36 weeks (alopecia areata). Risk of serious infections, MACE, thrombosis, and malignancy — requires full pre-treatment screening.

Paediatric dose

Route: Oral
Frequency: Once daily
Max: Not licensed in children <18 years for atopic eczema or alopecia areata in UK
Not currently licensed in paediatric patients in the UK for these indications. Specialist consideration only.

Dose adjustments

Renal

eGFR 30–60 mL/min: use 2 mg once daily. eGFR <30 mL/min: avoid use.

Hepatic

No dose adjustment in mild-moderate hepatic impairment. Avoid in severe hepatic impairment.

Clinical pearls

  • NICE TA878 (2023): baricitinib recommended for moderate-severe atopic eczema in adults when dupilumab unsuitable or response inadequate
  • BRAVE-AA1 and BRAVE-AA2 trials: baricitinib 4 mg OD produces ≥80% scalp hair regrowth (SALT score) in ~30–40% of severe alopecia areata patients at 36 weeks
  • Pre-treatment screening mandatory: TB (IGRA/Mantoux), hepatitis B/C serology, FBC, lipids, renal function, VZV antibody status (vaccinate seronegative patients before starting)
  • Herpes zoster risk: live zoster vaccine (Zostavax) is contraindicated during JAK inhibitor therapy — use recombinant Shingrix (inactive) if available before starting
  • MHRA/EMA class warning: JAK inhibitors carry boxed warning for serious cardiovascular events, malignancy, and thrombosis — discuss risks with patient; use lowest effective dose

Contraindications

  • Active serious infection (including active TB)
  • Absolute lymphocyte count <500 cells/mm³
  • Absolute neutrophil count <1000 cells/mm³
  • Haemoglobin <8 g/dL
  • Pregnancy
  • Severe renal impairment (eGFR <30 mL/min)

Side effects

  • Increased risk of serious infections (herpes zoster — reactivation, bacterial, TB)
  • MACE (major adverse cardiovascular events) — class effect of JAK inhibitors
  • Venous thromboembolism (DVT, pulmonary embolism) — class effect
  • Malignancy risk (non-melanoma skin cancer, lymphoma) — monitor
  • Elevated lipids (TC, LDL, HDL)
  • Elevated creatinine
  • Nasopharyngitis and URTI
  • Headache
  • Acne

Interactions

  • Strong OAT3 inhibitors (probenecid) — reduce baricitinib clearance; reduce dose to 2 mg OD
  • Live vaccines — contraindicated during and within 3 months of stopping
  • Other JAK inhibitors, biologics, or potent immunosuppressants — avoid combination (increased infection risk)

Monitoring

  • FBC (lymphocytes, neutrophils, haemoglobin) — at baseline, 4 weeks, then 3-monthly
  • LFTs and renal function — baseline then 3-monthly
  • Fasting lipids — baseline, 12 weeks, then annually
  • TB screening before starting
  • Herpes zoster and infection surveillance
  • Skin surveillance for NMSC
  • EASI/IGA score (eczema) or SALT score (alopecia areata) — response assessment at 16 weeks

Reference: BNFc; BNF; NICE TA878 (2023); BRAVE-AA1/AA2 Trials (King et al, NEJM 2022); MHRA JAK Inhibitor Safety Review; BAD Atopic Eczema Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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