Mechanism of action
Hydroxycarbamide decreases the production of deoxyribonucleotides via inhibition of the enzyme ribonucleotide reductase by scavenging tyrosyl free radicals as they are involved in the reduction of nucleoside diphosphates (NDPs).In the treatment of sickle-cell disease, hydroxycarbamide increases the concentration of fetal hemoglobin. The precise mechanism of action is not yet clear, but it appears that hydroxycarbamide increases nitric oxide levels, causing soluble guanylyl cyclase activation with a resultant rise in cyclic GMP, and the activation of gamma globin gene expression and subsequent gamma chain synthesis necessary for fetal hemoglobin (HbF) production (which does not polymerize and deform red blood cells like the mutated HbS, responsible for sickle cell disease). Adult red cells containing more than 1% HbF are termed F cells. These cells are progeny of a small pool of immature committed erythroid precursors (BFU-e) that retain the ability to produce HbF. Hydroxyurea also suppresses the production of granulocytes in the bone marrow which has a mild immunosuppressive effect particularly at vascular sites where sickle cells have occluded blood flow. Natural occurrence
Hydroxyurea has been reported as endogenous in human blood plasma at concentrations of approximately 30 to 200 ng/ml. Chemistry
Hydroxyurea has been prepared in many different ways since its initial synthesis in 1869. Medical chemists, Dresler and Stein created Hydroxyurea from hydroxylamine, hydrochloric acid and potassium cyanide as a technical exercise in organic chemistry, as part of a series of experiments generating derivatives of urea.
Hydroxycarbamide, also known as hydroxyurea, is a medication used in sickle-cell disease, essential thrombocythemia, chronic myelogenous leukemia and cervical cancer. In sickle-cell disease it increases fetal hemoglobin and decreases the number of attacks. It is taken by mouth.Common side effects include bone marrow suppression, fevers, loss of appetite, psychiatric problems, shortness of breath, and headaches. There is also concern that it increases the risk of later cancers. Use during pregnancy is typically harmful to the baby. Hydroxycarbamide is in the antineoplastic family of medications. It is believed to work by blocking the making of DNA.Hydroxycarbamide was approved for medical use in the United States in 1967. It is on the World Health Organizations List of Essential Medicines. Hydroxycarbamide is available as a generic medication. Medical uses
Hydroxycarbamide is used for the following indications:

Myeloproliferative disease (primarily essential thrombocythemia and polycythemia vera). It has been found to be superior to anagrelide for the control of ET. Sickle-cell disease (increases production of fetal hemoglobin that then interferes with the hemoglobin polymerisation as well as by reducing white blood cells that contribute to the general inflammatory state in sickle cell patients.)