What is Pacritinib: Uses, Dosage, Side Effects and More

Pacritinib is a targeted oral medication designed to help people with specific blood disorders, particularly a rare condition called myelofibrosis. This prescription drug works by blocking certain proteins that contribute to the progression of blood cancers, offering hope to patients who may have limited treatment options.

If you or someone you care about has been prescribed pacritinib, you're likely looking for clear, reliable information about what to expect. Let's walk through everything you need to know about this medication in a way that feels manageable and empowering.

What is Pacritinib?

Pacritinib is a specialized oral medication that belongs to a class of drugs called JAK inhibitors. It specifically targets proteins called Janus kinases, which play a role in how blood cells grow and function in your body.

The medication was developed specifically for people with myelofibrosis, a rare bone marrow disorder where healthy bone marrow tissue gets replaced by scar tissue. This process disrupts your body's ability to produce healthy blood cells normally.

What makes pacritinib unique among similar medications is that it can be safely used even when your platelet count is quite low. Many other treatments in this category require higher platelet levels, making pacritinib an important option for patients who might not qualify for other therapies.

What is Pacritinib Used For?

Pacritinib is primarily prescribed for adults with intermediate or high-risk primary myelofibrosis, post-polycythemia vera myelofibrosis, or post-essential thrombocythemia myelofibrosis. These are all forms of myelofibrosis, a condition where your bone marrow becomes scarred and can't produce blood cells effectively.

The medication is specifically indicated for patients whose platelet count is below 50,000 per microliter of blood. This low platelet count often makes other treatments unsuitable or unsafe, which is why pacritinib fills such an important gap in treatment options.

Your doctor might recommend pacritinib if you're experiencing symptoms like severe fatigue, enlarged spleen, bone pain, or night sweats related to your myelofibrosis. The goal is to help reduce these symptoms and improve your quality of life while managing the underlying condition.

How Does Pacritinib Work?

Pacritinib works by blocking specific enzymes called JAK1 and JAK2, which are overactive in myelofibrosis. Think of these enzymes as switches that have gotten stuck in the "on" position, causing your bone marrow to behave abnormally.

When pacritinib blocks these switches, it helps slow down the abnormal cell signaling that leads to bone marrow scarring and the uncomfortable symptoms you might be experiencing. This can help reduce spleen size, decrease inflammation, and improve your overall comfort.

As a targeted therapy, pacritinib is considered a moderately strong medication. It's specifically designed to work on the molecular level rather than affecting your entire system broadly. This targeted approach often means fewer side effects compared to traditional chemotherapy, though it's still a serious medication that requires careful monitoring.

How Should I Take Pacritinib?

Pacritinib comes as capsules that you take by mouth twice daily, approximately 12 hours apart. The typical starting dose is 200 mg twice daily, but your doctor will determine the exact dose that's right for your specific situation.

You can take pacritinib with or without food, but try to be consistent with your routine. If you choose to take it with food, stick with that pattern, and if you prefer taking it on an empty stomach, do that consistently. This helps maintain steady levels of the medication in your system.

Swallow the capsules whole with a full glass of water. Don't open, crush, or chew them, as this can affect how the medication is absorbed and may increase side effects. If you have trouble swallowing capsules, talk with your healthcare team about strategies that might help.

It's helpful to take your doses at the same times each day to establish a routine. Many people find it easier to remember when they link their medication times to daily activities like meals or bedtime routines.

How Long Should I Take Pacritinib For?

The duration of pacritinib treatment varies significantly from person to person and depends on how well you respond to the medication and how well you tolerate it. Some people may take it for months, while others might continue for years.

Your doctor will monitor your response through regular blood tests and physical examinations. They'll assess whether your symptoms are improving, if your spleen size is decreasing, and how your blood counts are responding to treatment.

The decision about how long to continue treatment will be based on the balance between the benefits you're experiencing and any side effects you might have. Your healthcare team will work with you to find the right approach for your individual situation.

Never stop taking pacritinib suddenly without discussing it with your doctor first. They may need to adjust your dose gradually or monitor you closely during any treatment changes.

What Are the Side Effects of Pacritinib?

Like all medications, pacritinib can cause side effects, though not everyone experiences them. Understanding what to watch for can help you feel more prepared and know when to reach out to your healthcare team.

The most common side effects tend to be manageable and often improve as your body adjusts to the medication. Here are the side effects you're most likely to encounter:

• Diarrhea, which can range from mild to moderate
• Nausea and occasional vomiting
• Swelling in your legs, ankles, or feet
• Fatigue or feeling more tired than usual
• Bruising more easily than normal
• Dizziness or feeling lightheaded
• Muscle or joint pain

These common side effects are usually temporary and can often be managed with supportive care or dose adjustments. Your healthcare team can provide specific strategies to help you feel more comfortable.

Less commonly, some people experience more serious side effects that require immediate medical attention. While these are rarer, it's important to be aware of them:

• Severe bleeding or unusual bruising
• Signs of infection like persistent fever or chills
• Severe diarrhea that leads to dehydration
• Significant swelling or difficulty breathing
• Heart rhythm changes or palpitations

If you experience any of these more serious symptoms, contact your healthcare provider right away. They can help determine whether these are related to your medication and what steps to take next.

Who Should Not Take Pacritinib?

Pacritinib isn't suitable for everyone, and your doctor will carefully evaluate whether it's the right choice for your specific situation. Certain medical conditions or circumstances may make this medication inappropriate or require special precautions.

People with severe liver problems should not take pacritinib, as the medication is processed through the liver and could potentially worsen liver function. Your doctor will check your liver function before starting treatment and monitor it regularly while you're taking the medication.

If you have a history of serious heart rhythm problems, your doctor will need to weigh the benefits and risks carefully. Pacritinib can affect heart rhythm in some people, so this requires close monitoring and consideration of alternative treatments.

Active, serious infections are another important consideration. Since pacritinib can affect your immune system's ability to fight infections, starting treatment during an active infection could be dangerous. Your doctor will want to treat any infections first before beginning pacritinib.

Pregnancy and breastfeeding require special consideration. Pacritinib could potentially harm a developing baby, so women of childbearing age need to use effective contraception during treatment and for some time after stopping the medication.

Pacritinib Brand Names

Pacritinib is available under the brand name Vonjo in the United States. This is the commercial name you'll see on your prescription bottle and medication packaging.

Vonjo was approved by the FDA specifically for treating myelofibrosis in patients with low platelet counts. If you see this name on your prescription, it's the same medication we've been discussing throughout this article.

Currently, pacritinib is only available as a brand-name medication. Generic versions are not yet available, which means the cost may be higher than medications that have generic alternatives.

Pacritinib Alternatives

Several other medications are available for treating myelofibrosis, though each has different requirements and considerations. Your doctor will help determine which option might be best for your specific situation.

Ruxolitinib (Jakafi) is another JAK inhibitor commonly used for myelofibrosis. However, it typically requires higher platelet counts than pacritinib, making it unsuitable for patients with very low platelets. This is one of the key differences between these two medications.

Fedratinib (Inrebic) is another option that works similarly to pacritinib but has different side effect profiles and requirements. Some people may tolerate one medication better than another, so having multiple options is valuable.

For some patients, other approaches like blood transfusions, medications to manage specific symptoms, or participation in clinical trials might be considered. The best choice depends on your overall health, blood counts, symptom severity, and personal preferences.

Is Pacritinib Better Than Ruxolitinib?

Pacritinib and ruxolitinib are both effective JAK inhibitors, but they serve different patient populations and have distinct advantages. The "better" choice depends entirely on your individual medical situation and needs.

The main advantage of pacritinib is that it can be used safely in patients with very low platelet counts (below 50,000). Ruxolitinib typically requires higher platelet levels, so pacritinib fills an important gap for patients who can't use other treatments.

Ruxolitinib has been available longer and has more extensive long-term data, which some doctors and patients find reassuring. It's also been studied in a broader range of conditions beyond myelofibrosis.

Side effect profiles differ between the two medications. Some people may tolerate one better than the other, and your doctor can help predict which might work better based on your medical history and current health status.

The decision between these medications should always be made in partnership with your healthcare team, taking into account your specific blood counts, symptoms, other medical conditions, and treatment goals.