Background: Although the platelet count may not always correlate with the risk of thrombosis, there is evidence that a strict control of the platelet count decreases the incidence of thrombotic and hemorrhagic complications. However, it is difficult to select an appropriate platelet-lowering agent. This retrospective study was performed to assess the efficacy and adverse effect of the use of hydroxyurea and anagrelide for patients with essential thrombocythemia. Methods: Sixty patients with essential thrombocythemia received either hydroxyurea (n=30) or anagrelide (n=30). Early responses and adverse effects of hydroxyurea and anagrelide in the patients were retrospectively analyzed. Results: Treatment with anagrelide or hydroxyurea resulted in a rapid decrease of the platelet count within two weeks. The response rates after treatment with hydroxyurea and anagrelide were 83% and 77%, respectively. As compared with patients treated with hydroxyurea, patients treated with anagrelide presented with adverse effects such as headache palpitation was also frequently noticed (P=0.001). However, serious hemorrhage (n=2) and transformation to leukemia (n=1) occurred in patients treated with hydroxyurea. Conclusion: Both anagrelide and hydroxyurea were effective and well-tolerated agents for the reduction of the platelet count. Long-term efficacy and adverse effects of the drugs remain to be determined. (Korean J Hematol 2008;43:83-88.)

Keywords: Essential thrombocythemia, Anagrelide, Hydroxyurea