Effect of Nplate (Romiplostim) on White Blood Cell Count
Romiplostim (Nplate) can affect white blood cell counts, with monitoring of WBC counts recommended during treatment, especially in patients with pre-existing hematologic conditions.
Mechanism and Primary Effects
Romiplostim (Nplate) is a thrombopoietin receptor agonist that primarily stimulates platelet production by binding to and activating the thrombopoietin receptor on megakaryocyte precursors 1. While its main therapeutic action is to increase platelet counts, its effects on bone marrow can extend beyond megakaryocytes.
Evidence for WBC Effects
The evidence regarding romiplostim's effects on white blood cell counts comes primarily from clinical guidelines and safety monitoring recommendations:
In patients receiving azathioprine or cyclophosphamide concurrently, monitoring of white blood cell counts is essential, as these medications should be reduced or stopped if WBC decreases to <4,000/mm³ 2.
Romiplostim has been studied extensively in thrombocytopenic conditions, with most adverse events being mild to moderate in severity, primarily focused on platelet-related outcomes rather than WBC effects 3.
When used in radiation countermeasure studies, romiplostim primarily affected platelet recovery, while "kinetic profiles of other hematology parameters [including WBC] were similar between treated and control mice" 4.
Clinical Considerations
Patient Populations at Risk
Patients with certain conditions may be at higher risk for WBC changes when taking romiplostim:
Patients with myelodysplastic syndrome (MDS): Romiplostim has been investigated for thrombocytopenia in MDS, where monitoring of all blood cell lines is important 2.
Patients receiving concurrent medications that affect bone marrow function: Special attention should be paid to white blood cell counts in these patients 2.
Monitoring Recommendations
Regular complete blood count (CBC) monitoring is essential during romiplostim therapy, with frequency depending on the underlying condition and treatment phase 5.
For patients with MDS receiving romiplostim, careful monitoring of all blood cell lines is recommended due to concerns about potential disease progression 2.
Clinical Implications
If WBC changes are observed during romiplostim treatment:
Evaluate for other causes of WBC changes (infection, concurrent medications, underlying disease progression).
Consider dose adjustment of romiplostim or concurrent medications that affect bone marrow function.
In patients with MDS, monitor for signs of disease progression, as romiplostim's effects on disease course have been studied with mixed results 2.
Summary
While romiplostim primarily affects platelet production, its action on bone marrow progenitor cells means it has the potential to affect white blood cell production in some patients. Regular monitoring of complete blood counts is recommended during treatment, particularly in patients with pre-existing hematologic disorders or those on concurrent medications affecting bone marrow function.