Pacritinib (Vonjo) is a kinase inhibitor indicated for the treatment of intermediate- or high-risk primary or secondary (post-polycythemia vera or post-essential thrombocythemia) myelofibrosis in patients with a platelet count below 50×10⁹/L.

Precautions for Pacritinib (Vonjo) Administration

1. Bleeding Risk Management

(1) Pacritinib can cause severe or even life-threatening bleeding, which is more common especially in patients with a platelet count < 100×10⁹/L.

(2) Before initiating treatment, assess the patient’s bleeding risk; avoid use in patients with active bleeding.

(3) Discontinue the drug 7 days before any elective surgery or invasive procedure, and resume use only after hemostasis is confirmed.

(4) During treatment, regularly monitor platelet count and coagulation function. In case of moderate to severe bleeding, immediately discontinue the drug and initiate medical intervention.

2. Prevention and Management of Diarrhea

(1) Approximately 48% of patients experience diarrhea, among which 4% develop grade 3–4 severe diarrhea.

(2) Pre-existing diarrhea symptoms should be controlled before treatment initiation, and antidiarrheal medications (e.g., loperamide) should be prescribed concurrently with pacritinib.

(3) Patients must start antidiarrheal treatment immediately upon the first occurrence of changes in stool frequency or consistency, and maintain adequate fluid intake.

(4) For persistent or severe diarrhea, consider dosage adjustment or treatment interruption, while being alert to acute kidney injury caused by diarrhea.

3. Monitoring of QT Interval Prolongation

(1) Pacritinib may cause prolongation of the QTc interval; avoid use in patients with a baseline QTc interval > 480 ms.

(2) Before treatment, complete a baseline electrocardiogram (ECG), correct hypokalemia, and avoid concurrent use of other drugs that may prolong the QT interval.

(3) If a QTc interval > 500 ms or an increase of > 60 ms from baseline occurs during treatment, immediately discontinue administration. Resume treatment at a reduced dose only after the QTc interval returns to normal.

4. Patients with Hepatic Impairment

(1) The recommended dose for patients with severe hepatic impairment (Child-Pugh Class C) is 100 mg twice daily.

(2) If there are no safety concerns and the therapeutic effect is insufficient after 12 weeks of treatment, the dose may be increased to the standard dose (200 mg twice daily).

(3) Patients with mild to moderate hepatic impairment do not require dose adjustment, but still need close monitoring for adverse reactions.

5. Reproductive-Age Population

(1) Use during pregnancy may cause harm to the fetus. Women of reproductive age should use effective contraceptive measures during treatment and for 4 months after the last dose.

(2) Note that pacritinib may reduce the efficacy of hormonal contraceptives; it is recommended to use an intrauterine device (IUD) or other non-hormonal contraceptive methods.

(3) Lactating women should discontinue breastfeeding until 2 weeks after the last dose.

Medication Monitoring for Pacritinib (Vonjo)

1. Laboratory Monitoring

(1) Before treatment, complete a full blood count (including white blood cell differential and platelet count), coagulation function tests, and a baseline ECG.

(2) During treatment, conduct regular monitoring: full blood count once a month, continuing until 48 months after the last dose.

(3) Thyroid function tests once every 3 months; annual skin examinations to screen for melanoma.

2. Key Adverse Reaction Monitoring

(1) Hematological System: Focus on thrombocytopenia. Monthly monitoring enables early detection; emergency intervention is required if the platelet count ≤ 20,000/μL.

(2) Cardiovascular System: Patients who are current or former smokers, or those with cardiovascular risk factors, need to be alert to major adverse cardiovascular events (MACE).

(3) Infection Monitoring: Delay treatment in cases of active severe infection. Closely monitor for signs of infection during medication use; if necessary, administer prophylactic anti-infective treatment in accordance with clinical guidelines.