What is the recommended dose of Romiplostim (romiplostim) for an adult or pediatric patient with chronic immune thrombocytopenia (ITP)?

Romiplostim Dosing for Immune Thrombocytopenia

Initial Dosing

Start romiplostim at 1 mcg/kg subcutaneously once weekly for both adults and pediatric patients (≥1 year old) with chronic ITP. 1, 2

• The American Society of Hematology recommends this initial dose with subsequent weekly adjustments based on platelet response to achieve and maintain platelet counts ≥50 × 10^9/L 1
• The maximum dose should not exceed 10 mcg/kg per week 1, 2
• Administer as a subcutaneous injection once weekly 2

Dose Titration Strategy

Adjust the dose weekly by increments of 1 mcg/kg until platelet counts reach ≥50 × 10^9/L: 1

• If platelet count remains <50 × 10^9/L: Increase dose by 1 mcg/kg weekly 1
• If platelet count exceeds 200 × 10^9/L: Temporarily withhold romiplostim until platelet count falls below 200 × 10^9/L, then resume at a reduced dose 1
• Target platelet range: Maintain counts between 50-200 × 10^9/L 1
• If no response after 4 weeks at maximum dose (10 mcg/kg): Discontinue romiplostim as ineffective 1

Monitoring Requirements

Monitor platelet counts weekly during dose adjustment phase until stable counts are achieved: 1

• Weekly complete blood counts with platelet counts are required until a stable dose is established 1
• Once platelet counts stabilize (≥50 × 10^9/L for at least 4 weeks without dose adjustment), reduce monitoring frequency to monthly 1
• Platelet response typically occurs within 1-4 weeks in patients with baseline counts <30 × 10^9/L 1
• Overall response rates are 88% in non-splenectomized patients and 79% in splenectomized patients 1

Tapering and Discontinuation Protocol

For patients with stable responses maintained for ≥6 months, consider gradual tapering: 1

• Reduce romiplostim by 1 mcg/kg/week every 2 weeks until reaching 1 mcg/kg/week 1
• Then administer 1 mcg/kg every other week for 2-3 administrations 1
• Follow with once every 3 weeks before complete discontinuation 1
• Monitor closely for rebound thrombocytopenia upon discontinuation, as worsening thrombocytopenia may occur with abrupt cessation 1
• Approximately 30% of patients may achieve sustained remission lasting ≥6 months after discontinuation 3, 1

Critical Safety Considerations

Exercise caution in patients with preexisting thrombotic risk factors: 1

• Thrombotic events occurred in 6.5% of patients in long-term studies 1, 4
• Common adverse events (≥20% of patients) include headache, fatigue, epistaxis, arthralgia, and contusion 1
• Bone marrow reticulin formation can occur but is typically mild, asymptomatic, and reversible upon treatment interruption 1
• Monitor liver function tests, as abnormalities have been reported with TPO receptor agonists 1

Important Clinical Pitfalls

Avoid abrupt discontinuation without tapering: 1

• Rebound thrombocytopenia is a recognized serious adverse event that can occur with sudden cessation 1
• Most patients require continuous maintenance therapy, as romiplostim works through ongoing platelet production stimulation 1
• In overdose situations where platelet counts increase excessively, discontinue temporarily and monitor platelet counts before reinitiating at appropriate doses 2

Pediatric Considerations

The same weight-based dosing applies to pediatric patients ≥1 year old: 2

• Safety and effectiveness are established in pediatric patients ≥1 year with ITP lasting ≥6 months 2
• Serum concentrations in pediatric patients are within the range observed in adults receiving the same dose 2
• Romiplostim is not established as safe or effective in pediatric patients <1 year old 2