Chronic Myeloid Leukemia (CML):

  • Adults: 20–30 mg/kg/day orally
  • Adjust according to white blood cell (WBC) response

 Sickle Cell Anemia (SCA):

  • Adults & children >2 years: Initial dose 15 mg/kg/day (10 mg/kg/day in renal impairment)
  • Increase by 5 mg/kg every 12 weeks up to maximum 35 mg/kg/day
  • Monitor blood counts regularly

 Polycythemia Vera & Essential Thrombocythemia:

  • Starting dose: ~15–20 mg/kg/day
  • Adjust based on hematologic response

 Head & Neck Cancer (in combination with radiation):

  • 80 mg/kg every 3 days orally
  • Begin 7 days before radiotherapy
  • Capsules: 200 mg, 300 mg, 400 mg, 500 mg
  • Tablets (e.g., Siklos): 100 mg, 1,000 mg (scored for pediatric dosing)
  • Take with or without food, preferably at the same time daily.
  • Swallow whole; do not crush or open capsules (cytotoxic).
  • Adequate hydration is important to reduce GI irritation and prevent uric acid build-up.

Mechanism of Action:

  • Inhibits ribonucleotide reductase, blocking DNA synthesis in the S-phase of the cell cycle.
  • In sickle cell disease, increases fetal hemoglobin (HbF) levels, reducing sickling and vaso-occlusive crises.

Pharmacokinetics:

  • Absorption: Rapid, nearly complete
  • Half-life: ~3–4 hours
  • Metabolism: Liver (partial)
  • Excretion: Primarily renal
  • Bone marrow suppression (neutropenia, thrombocytopenia, anemia)
  • Gastrointestinal: nausea, vomiting, diarrhea, constipation
  • Mucositis
  • Fever
  • Skin ulcerations
  • Hyperpigmentation or rash
  • Elevated liver enzymes, creatinine, or BUN
  • Hypersensitivity to hydroxyurea
  • Severe bone marrow depression
  • Pregnancy (especially 1st trimester)
  • Breastfeeding
  • Antiretroviral agents (especially didanosine, stavudine): Increased risk of pancreatitis, hepatotoxicity, and neuropathy
  • Myelosuppressive agents: Additive effects on bone marrow suppression
  • Live vaccines: Avoid due to immunosuppressive effects

                                   Drug Status

Availability
Pregnancy
Breastfeeding
Schedule
BRAND NAME STRENGTH FORMULATION PACK SIZE MANUFACTURER DISTRIBUTOR
Riborea 500mg Capsule 100’s PSM Pharma PSM Pharma