Mylostat

Hydroxyurea is indicated for the treatment of resistant chronic myeloid leukemia, locally advanced squamous cell carcinomas of the head and neck (excluding the lip) in combination with chemoradiation.

Cytotoxic Chemotherapy

Hydroxyurea is converted to a free radical nitroxide (NO) in vivo, and transported by diffusion into cells where it quenches the tyrosyl free radical at the active site of the M2 protein subunit of ribonucleotide reductase, inactivating the enzyme. The entire replicase complex, including ribonucleotide reductase, is inactivated and DNA synthesis is selectively inhibited, producing cell death in S phase and synchronization of the fraction of cells that survive. Repair of DNA damaged by chemicals or irradiation is also inhibited by hydroxyurea, offering potential synergy between hydroxyurea and radiation or alkylating agents. Hydroxyurea also increases the level of fetal hemoglobin, leading to a reduction in the incidence of vasoocclusive crises in sickle cell anemia. Levels of fetal hemoglobin increase in response to activation of soluble guanylyl cyclase (sGC) by hydroxyurea-derived NO.

Malignancies Chronic myeloid leukaemia: 20-30 mg/kg/day.

Solid tumours: 80 mg/kg every third day. With radiotherapy, start treatment 7 days before initiation of radiotherapy.

Sickle-cell disease: Initial: 15 mg/kg/day. Max: 35 mg/kg/ day. Adjust based on response and blood counts.

Essential thrombocythemia: 15 mg/kg/day. Adjust based on platelet counts.

Gl disturbances, Nausea, Vomiting, Constipation, Diarrhea, Hyperuricemia, Renal failure, Rash, Hyperpigmentation. Pulmonary oedema, dermatological reactions, headache, dizziness. Disorientation, drowsiness, hallucinations, convulsions, alopecia.

Severe bone-marrow suppression, severe anaemia, WBC <3000/mm3 or platelet count <100,000/mm3. Pregnancy and lactation. Hypersensitivity.

Regular monitoring of uric acid concentrations, blood counts, renal and hepatic function is recommended. Prior irradiation therapy. Elderly. Avoid use of live vaccines.

Impairs immune response to vaccines; possible infection with live vaccines, zidovudine, zalcitabine. May alter action of oral anticoagulants and phenytoin.

Pregnancy category D. There is positive evidence of human fetal risk based on adverse reaction data from investigational or marketing experience or studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.

Lactation: Excreted in breast milk, do not nurse