Hydroxyurea and Thrombocytopenia
Yes, hydroxyurea can cause thrombocytopenia as a known side effect, particularly when used at doses required for clinical response in myeloproliferative disorders. 1
Mechanism and Evidence
- Hydroxyurea is a cytoreductive agent that causes bone marrow suppression, which can affect all cell lines including platelets 2
- The European LeukemiaNet and NCCN guidelines specifically identify thrombocytopenia as a recognized adverse effect of hydroxyurea therapy 1
- Platelet counts <100 x 10^9/L at the lowest dose of hydroxyurea required to achieve clinical response is considered a criterion for hydroxyurea intolerance in polycythemia vera 1
- Bone marrow depression is more likely in patients who have previously received radiotherapy or cytotoxic cancer chemotherapeutic agents 2
Clinical Significance
- Thrombocytopenia is less common than leukopenia, which is generally the first and most common manifestation of hydroxyurea-induced myelosuppression 2
- In patients with myeloproliferative disorders, the development of thrombocytopenia (platelet count <100 x 10^9/L) is considered a criterion for intolerance to hydroxyurea and may necessitate dose reduction or discontinuation 1
- Recovery from hydroxyurea-induced myelosuppression, including thrombocytopenia, is usually rapid when therapy is interrupted 2
Monitoring Recommendations
- Complete blood counts should be monitored at least weekly during initial hydroxyurea therapy and every 4-8 weeks once stabilized 3, 2
- Evaluate hematologic status prior to and during treatment with hydroxyurea 2
- Bone marrow function should not be markedly depressed before initiating hydroxyurea therapy 2
Management of Hydroxyurea-Induced Thrombocytopenia
- If platelet count falls below 100 x 10^9/L, consider dose reduction or temporary discontinuation of hydroxyurea 1
- Provide supportive care as needed for significant thrombocytopenia 2
- For patients with persistent thrombocytopenia despite dose adjustments, consider alternative cytoreductive agents:
Special Considerations
- In rare cases, hydroxyurea can cause hemolytic anemia rather than myelosuppressive anemia, which may complicate the clinical picture 5
- Patients with beta-thalassemia treated with hydroxyurea may develop transient thrombocytopenia that resolves after temporary discontinuation 6
- The risk of hydroxyurea-induced thrombocytopenia must be balanced against its proven benefits in reducing thrombotic complications in high-risk essential thrombocythemia patients 7, 8
Remember that while hydroxyurea can cause thrombocytopenia, it is generally well-tolerated and remains a first-line cytoreductive therapy for myeloproliferative disorders when indicated 1, 3.