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JAK Inhibitor (JAK1/JAK3 Inhibitor)

Tofacitinib

Brand names: Xeljanz

Tofacitinib is an oral Janus kinase (JAK) inhibitor used in gastroenterology to treat moderate-to-severe ulcerative colitis.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

Clinical monograph

How it works

It inhibits JAK enzymes, interrupting cytokine signalling through the JAK-STAT pathway and thereby reducing the inflammatory response in the colonic mucosa.

Prescribing in practice

  • MHRA advice restricts use in patients at risk of venous thromboembolism, major cardiovascular events, serious infection, or malignancy, and the lowest effective dose should be used in these groups.
  • Screen for tuberculosis and viral hepatitis before starting, avoid live vaccines, and consider herpes zoster vaccination given the increased risk of shingles.
  • It can raise lipids and liver enzymes and cause cytopenias, which require baseline and ongoing assessment per the SPC.

Monitoring

Monitor full blood count, lipids, and liver function during treatment, and remain vigilant for infection and thromboembolic events.

Counselling the patient

  • Report signs of infection, shingles, or symptoms of a clot such as leg swelling or chest pain.
  • Attend for the blood tests needed to monitor your blood counts, cholesterol, and liver.

Evidence & guidelines

An MHRA safety review led to restricted use of tofacitinib in patients with cardiovascular, thromboembolic, or malignancy risk factors.

Reference: NICE TA480; ORAL Surveillance trial; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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