Hydroxycarbamide, also known as hydroxyurea, is an antimetabolite medication used in sickle-cell disease, essential thrombocythemia, chronic myelogenous leukemia, polycythemia vera, and cervical cancer.

[4] Common side effects include bone marrow suppression, fevers, loss of appetite, psychiatric problems, shortness of breath, and headaches.

[4] Hydroxycarbamide is used for the following indications: Reported side effects are: neurological reactions (e.g., headache, dizziness, drowsiness, disorientation, hallucinations, and convulsions), nausea, vomiting, diarrhea, constipation, mucositis, anorexia, stomatitis, bone marrow toxicity (dose-limiting toxicity; may take 7–21 days to recover after the drug has been discontinued), megaloblastic anemia, thrombocytopenia, bleeding, hemorrhage, gastrointestinal ulceration and perforation, immunosuppression, leukopenia, alopecia (hair loss), skin rashes (e.g., maculopapular rash), erythema, pruritus, vesication or irritation of the skin and mucous membranes, pulmonary edema, abnormal liver enzymes, creatinine and blood urea nitrogen.

[12] Due to its negative effect on the bone marrow, regular monitoring of the full blood count is vital, as well as early response to possible infections.

[15] Hydroxycarbamide decreases the production of deoxyribonucleotides[16] via inhibition of the enzyme ribonucleotide reductase by scavenging tyrosyl free radicals as they are involved in the reduction of nucleoside diphosphates (NDPs).

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).

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.

[26] Hydroxyurea has many pharmacological applications under the Medical Subject Headings classification system:[24] Brand names include: Hydrea, Litalir, Droxia, and Siklos.