The effect of hydroxyurea on hemoglobin F in patients with myeloproliferative syndromes.

Fetal hemoglobin (Hb F) may increase in patients receiving chemotherapeutic drugs, a result of potential use in patients with symptomatic hemoglobinopathies. We examined Hb F in 13 patients with myeloproliferative disease (six polycythemia vera, five polycythemia vera with myeloid metaplasia, one agnogenic myeloid metaplasia, and one chronic myelogenous leukemia) who were treated with hydroxyurea. Four patients showed an increase in Hb F from less than 1% to between 5% and greater than 8% while on hydroxyurea, and a decline to less than 1% when the drug was discontinued. This group of "responders" received a higher average daily dose of hydroxyurea, which was administered continuously rather than intermittently, when compared to the "nonresponders." Mean corpuscular volumes (MCVs) rose in most patients, and i antigen remained elevated or decreased; neither parameter correlated with Hb F levels. Both responders and nonresponders had therapeutically desirable suppression of WBCs and platelets, and almost all had no depression of reticulocytes or Hb.