Hydroxyurea 500mg Capsules are used to treat cancer of the white blood cells called chronic myeloid leukemia (CML It may also be given together with radiation treatment for head and neck cancer (advanced squamous cell cancer. Hydroxyurea interferes with the growth of cancer cells, which are eventually destroyed by the body13. Hydroxyurea is also used by people with sickle cell anemia to reduce the number of painful crises caused by the disease and to reduce the need for blood transfusions