Hydroxyurea is a specialty chemical reagent, commonly used in biotechnology and pharmaceutical research as an inhibitor of ribonucleotide reductase, which blocks DNA synthesis and arrests cells in the S-phase of the cell cycle. Clinically, it is primarily used in the treatment of certain types of cancer, particularly chronic myelogenous leukemia (CML). It works by slowing down the growth of cancer cells, allowing the body to manage the disease more effectively. Additionally, it is used to manage sickle cell anemia by increasing the production of fetal hemoglobin, which reduces the frequency of painful crises and the need for blood transfusions. In some cases, it is also employed to treat essential thrombocythemia, a condition characterized by an overproduction of platelets, helping to reduce the risk of blood clots.