The July 7, 2005 issue of NEJM reports a RCT in which cases of essential thrombocythemia at risk for thrombosis were treated with either hydroxyurea plus ASA or anagrelide plus ASA. The hydroxyurea arm was better in almost everyway. There were fewer arterial thromboses, fewer serious hemorrhages and fewer withdrawals from therapy in the hydroxyurea group while the anagrelide group had fewer venous thromboses. Essential thrombocythemia manages to pose a risk of both hemorrhage and thrombosis, the former occurring at the higher platelet counts. Concern about the potential leukemogenic effect of alkalating agents lead to the development and clinical application of anagrelide which apparently only affects the platelets, doing little or no harm to the red and white cells. Anagrelide seemed a reasonable replacement from hydroxyurea. However, this RCT strongly suggests otherwise. This was the first head- to- head comparison of the two treatments and although urea was not better in every measured way,
on balance it appears a better choice.