Clinical Guide for Promacta (eltrombopag)

About

The Promacta (eltrombopag) dosing calculator is a support tool designed for healthcare professionals to determine the appropriate starting dose of eltrombopag based on patient-specific factors. It considers the approved indication, patient age, ancestry, and degree of hepatic impairment to provide a recommended initial dosing schedule in line with FDA-approved guidelines.

Outputs

After entering the required patient parameters, the calculator provides a comprehensive output summary, which includes:

• Recommended Starting Dose: The initial daily dose in milligrams (mg) or mg/kg for specific pediatric populations.
• Rationale for Adjustment: A clear explanation if the dose was modified from the standard, for example, due to ancestry or hepatic impairment.
• Maximum Dose: The maximum allowable daily dose for the selected indication.
• Titration Guidance: General principles for dose adjustment based on platelet response to achieve therapeutic goals.
• Key Monitoring Parameters: A list of essential laboratory and clinical monitoring, including CBC, LFTs, and ophthalmologic exams.
• Administration Counseling: Crucial instructions regarding food and cation interactions.

How to Use

To use the calculator effectively, follow these steps:

1. Select Indication for Use: Choose the appropriate condition from the dropdown menu (e.g., ITP, SAA).
2. Specify Patient Age: Select either adult or pediatric. If pediatric, specify the correct age range.
3. Indicate Patient Ancestry: Select 'East or Southeast Asian' if applicable, as this may require a dose reduction.
4. Define Hepatic Impairment: Use the Child-Pugh score to select the level of liver function (None, Mild, Moderate, or Severe).
5. Enter Platelet Count (Optional): Inputting the current platelet count can provide context but does not alter the initial starting dose calculation.
6. Calculate Dosing: Click the "Calculate Dosing" button to generate the results.

Dosing Overview

Eltrombopag dosing is highly individualized. The initial dose depends on several factors, with subsequent adjustments made based on platelet count response. Key principles include:

• Standard Starting Doses:
  • Immune Thrombocytopenia (ITP): 50 mg once daily (for most patients ≥6 years).
  • Severe Aplastic Anemia (SAA) - First-Line: 150 mg once daily (for adults/adolescents).
  • Severe Aplastic Anemia (SAA) - Refractory: 50 mg once daily.
  • HCV-Related Thrombocytopenia: 25 mg once daily.
• Dose Reductions: A reduced starting dose is required for patients of East/Southeast Asian ancestry and for patients with moderate to severe hepatic impairment (in certain indications) due to increased drug exposure.
• Titration: Doses are typically adjusted every 2 weeks to achieve and maintain the target platelet count needed to reduce the risk of bleeding.

Switching

Switching a patient to eltrombopag from another thrombopoietin receptor agonist (TPO-RA) like romiplostim or avatrombopag requires careful clinical management. There are no standardized, universally accepted switching protocols. Clinical judgment is paramount, and decisions should be based on the patient's platelet count, bleeding risk, and the pharmacokinetic/pharmacodynamic properties of both agents. A washout period may or may not be necessary. Always consult the full prescribing information and relevant clinical guidelines when considering a switch.

Missed Dose

If a patient misses a dose of Promacta, they should not take an extra dose to make up for it. They should take the next scheduled dose at its regular time. Doubling up on doses can increase the risk of adverse effects.

Safety Alerts

FAQ

Why does patient ancestry affect the Promacta dose?
Patients of East or Southeast Asian ancestry have been shown to have higher eltrombopag plasma concentrations compared to other populations. To reduce the risk of toxicity, a lower starting dose is recommended.

What is the Child-Pugh score?
The Child-Pugh score is a clinical tool used to assess the severity of chronic liver disease. It's based on five factors: bilirubin, albumin, INR, ascites, and encephalopathy. The score (Class A, B, or C) determines if a reduced starting dose of Promacta is needed for certain indications.

How does the calculator handle hepatic impairment for SAA?
For refractory SAA, the calculator recommends a reduced starting dose for moderate to severe hepatic impairment. However, for first-line SAA in adults, the prescribing information does not recommend an initial dose modification, though close monitoring is critical. The tool reflects this nuance.

Does this tool calculate ongoing dose adjustments?
No. The calculator only provides the recommended starting dose. It also provides the general principles for titration (e.g., "adjust every 2 weeks"), but all subsequent dose adjustments must be based on serial platelet counts and clinical judgment.

What is the maximum dose for Promacta?
The maximum dose varies by indication. It is 75 mg/day for ITP, 150 mg/day for SAA, and 100 mg/day for HCV-related thrombocytopenia. The calculator output specifies the correct maximum dose for the selected condition.

Why must Promacta be taken away from food and dairy?
Eltrombopag binds tightly to polyvalent cations like calcium, iron, magnesium, and aluminum. This binding prevents the drug from being absorbed into the bloodstream. It must be taken at least 2 hours before or 4 hours after any foods (like dairy), antacids, or mineral supplements containing these cations.

Can I use this calculator for a child under 1 year of age?
No. The calculator and the approved prescribing information for Promacta cover pediatric patients aged 1 year and older for ITP. Dosing for infants under 1 has not been established.

Is Promacta approved for pediatric patients with Hepatitis C?
No. The use of Promacta for thrombocytopenia associated with chronic Hepatitis C is not indicated in pediatric patients. The calculator will display an error if this combination is selected.

References

1. PROMACTA® (eltrombopag) Prescribing Information. U.S. Food and Drug Administration.
2. Promacta® (eltrombopag) Healthcare Professional Site. Novartis.
3. Revolade (eltrombopag) Summary of Product Characteristics (SmPC). European Medicines Agency.
4. Neunert C, Terrell DR, Arnold DM, et al. 2019 American Society of Hematology guidelines for immune thrombocytopenia. Blood Adv. 2019;3(23):3829-3866.