Hydroxyurea is a chemotherapy agent with potent effects on the bone marrow. The agent was used for many years to treat people with certain malignancies before being used for sickle cell disease. The primary side-effect of hydroxyurea is suppression of blood counts, particularly the white blood cells (neutropenia) and platelets (thrombocytopenia).
It has been used in patients with recurrent vaso-occlusive crisis. Hydroxyurea increases fetal hemoglobin (HbF) production and slightly raises the total hemoglobin concentration in the body. Fetal hemoglobin reduces the chance that red blood cells will sickle in a person with sickle cell disease. Usual duration of treatment is 6-9 months as long term complications are not known.