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JAK1/2 Inhibitor

Ruxolitinib

Brand names: Jakavi

Ruxolitinib is an oral JAK1/JAK2 inhibitor used in myelofibrosis, polycythaemia vera resistant or intolerant to hydroxycarbamide, and graft-versus-host disease.

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 Janus kinases JAK1 and JAK2, blocking dysregulated cytokine and growth-factor signalling that drives myeloproliferation and inflammation.

Prescribing in practice

  • Causes dose-dependent myelosuppression (anaemia and thrombocytopenia), so blood counts must guide initiation and dose adjustment, and abrupt discontinuation should be avoided to prevent a cytokine-rebound flare.
  • Increases the risk of serious infections (including reactivation of tuberculosis, hepatitis B, and herpes zoster); screen and manage accordingly before and during treatment.
  • Dose reduction is required in renal or hepatic impairment and when co-prescribed with strong CYP3A4 inhibitors.

Monitoring

Monitor full blood count regularly, watch for signs of infection, and assess lipids and skin for non-melanoma malignancies periodically.

Counselling the patient

  • Do not stop the medicine suddenly without specialist advice, as symptoms can rebound quickly.
  • Report fever or other signs of infection without delay.
  • Attend regular blood tests so the dose can be adjusted safely.

Evidence & guidelines

Ruxolitinib's benefit in myelofibrosis was established in the COMFORT trials, and it is recommended by NICE for selected patients.

Reference: COMFORT-I (NEJM 2012); COMFORT-II (JCO 2012); NICE TA386; SPC Jakavi; 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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