Pacritinib is used to treat myelofibrosis with low platelets. During treatment, various adverse reactions may occur, and monitoring should focus on bleeding, gastrointestinal, and cardiovascular events.

I. Bleeding and Hematologic Adverse Reactions

1. Bleeding

Pacritinib can cause severe or even fatal bleeding, especially in patients with low platelets, who are at higher risk.

Manifestations include abnormal bleeding, bruising, epistaxis, and conjunctival hemorrhage.

Avoid use in patients with active bleeding.

Discontinue the drug at least 7 days before planned surgery or invasive procedures, and resume only after hemostasis is confirmed.

Seek medical attention immediately for bleeding that cannot be stopped.

2. Thrombocytopenia

It can cause further decreases in platelets and increase bleeding risk.

Complete blood counts should be monitored regularly before and during treatment.

If platelets worsen significantly and persistently, hold the drug and restart at half the previous dose after recovery.

If it recurs, hold again and reduce the dose.

3. Anemia and Neutropenia

Anemia may present as fatigue and pallor, and some patients require dose reduction or treatment interruption.

Neutropenia can increase infection risk, and blood counts should be monitored.

II. Gastrointestinal and Other Common Adverse Reactions

1. Diarrhea

Diarrhea is one of the most common adverse reactions of pacritinib.

It often occurs early in treatment and may gradually lessen with longer drug exposure.

Severe diarrhea can cause dehydration and lead to acute kidney injury.

An antidiarrheal medication should be prescribed in advance at treatment initiation and taken immediately if stools become loose or more frequent.

Drink more water to replace fluids; severe or persistent diarrhea requires prompt medical attention and, if necessary, suspension or dose reduction.

2. Nausea and Vomiting

It can cause nausea and vomiting, affecting eating and medication intake.

Eat small meals more frequently and avoid taking the drug on an empty stomach to reduce discomfort.

If symptoms are severe, inform the physician; dosage adjustment or symptomatic treatment may be needed.

3. Peripheral Edema

It may present as swelling of the ankles, legs, or feet.

It is usually mild, but if obvious or worsening, inform the physician for evaluation.

4. Other Common Reactions

These include dizziness, fever, dyspnea, pruritus, upper respiratory tract infection, and cough.

Most are mild to moderate and may resolve with symptomatic treatment or dosage adjustment.

III. Cardiovascular, Infectious, and Other Serious Adverse Reactions

1. QT Interval Prolongation

Pacritinib can cause QTc interval prolongation and increase the risk of arrhythmia.

Avoid use in patients with a baseline QTc exceeding 480 milliseconds.

Correct hypokalemia before and during treatment.

Seek medical attention immediately if dizziness, syncope, or palpitations occur.

If QTc is significantly prolonged, hold the drug; after recovery, restart at a reduced dose or the original dose as appropriate.

2. Major Adverse Cardiovascular Events

Other JAK inhibitors of the same class can increase the risk of cardiovascular death, myocardial infarction, and stroke in patients with rheumatoid arthritis.

Risk may be higher in current or past smokers and those with other cardiovascular risk factors.

Assess individual benefits and risks before use.

Seek medical attention immediately if symptoms such as chest pain, shortness of breath, unilateral weakness, or slurred speech occur.

3. Thrombosis

Deep vein thrombosis, pulmonary embolism, and arterial thrombosis may occur.

Manifestations include unilateral leg swelling and pain, sudden chest pain, and difficulty breathing.

If related symptoms occur, evaluate and treat as soon as possible.

4. Secondary Malignancies

Other JAK inhibitors of the same class can increase the risk of lymphoma and other malignancies, excluding non-melanoma skin cancer.

Risk is further increased in current or past smokers.

In patients with known malignancy, weigh benefits and risks before use.

5. Infection

Serious bacterial, mycobacterial, fungal, and viral infections may occur.

Starting treatment should be delayed until active serious infection is controlled.

During treatment, observe for signs of infection and use prophylactic anti-infective therapy when necessary.

Inform the physician promptly if symptoms such as fever, chills, fatigue, or rash occur.

6. Symptom Flare After Discontinuation

After interruption or discontinuation of pacritinib, myelofibrosis symptoms may worsen.

Manifestations may include fever, dyspnea, hypotension, night sweats, and pain in the left upper abdomen or left shoulder.

Do not interrupt or stop the drug on your own; gradual dose reduction should be done under physician guidance.