Hydroxyurea affects certain cells in the body, such as cancer cells or sickled red blood cells. Hydroxyurea is used to treat chronic myelocytic leukemia, ovarian cancer, and certain types of skin cancer (melanoma and primary squamous cell cancer of the head and neck). Hydroxyurea is also used to reduce pain episodes and the need for blood transfusions in people with sickle cell anemia. Hydroxyurea will not cure sickle cell anemia. Hydroxyurea may also be used for purposes not listed in this medication guide.