Pacritinib is a JAK2/IRAK1 inhibitor used to treat myelofibrosis with severe thrombocytopenia, and strict adherence to dosage regimens and monitoring of hematological toxicity are required. Its therapeutic effect is significant, but caution should be taken against risks such as bleeding and cardiac toxicity. Individualized adjustments are needed for medication in special populations.

1. Usage and dosage

(1) Standard dose: 200mg orally twice a day, on an empty stomach or with food. The whole pill should not be opened when swallowed, and can be replenished within 4 hours after leakage. If it exceeds the limit, it should be skipped.

(2) Dose adjustment: When platelet count is less than 50 × 10 ⁹/L, reduce to 100mg twice a day; Discontinue administration due to grade 3 non hematological toxicity, and reduce dosage by 50% after recovery.

2 Clinical efficacy

(1) Spleen volume reduction: Phase III trials showed that 35% of patients had a spleen volume reduction of ≥ 35%, with a median duration of response of 12.3 months.

(2) Symptom improvement: The proportion of patients with a total symptom score reduction of ≥ 50% reached 27%, including relief of symptoms such as night sweats and bone pain.

3 Precautions

(1) Blood monitoring: Complete blood cell count should be checked before treatment and every 2 weeks. Medication should be suspended if there is grade 3 or above anemia or thrombocytopenia.

(2) Cardiac risk: If the baseline QTc is greater than 450ms, medication should be avoided in combination with drugs that prolong the QT interval. If palpitations or fainting occur, medication should be stopped immediately.

(3) Bleeding management: Stop medication 7 days before surgery and avoid using antiplatelet drugs. The incidence of gastrointestinal bleeding is about 8%, and caution should be taken.

4 Special populations

(1) Liver damage patients: Child Pugh B grade reduced to 100mg twice daily, C grade contraindicated. Renal function does not require adjustment.

(2) Pregnant breastfeeding: It is prohibited during pregnancy, and women of childbearing age should use contraception until one month after discontinuing the medication. Suspend feeding during lactation.