How to Administer Hydroxyurea Orally
For a 70-kg adult, start hydroxyurea at 1050 mg (15 mg/kg) once daily by mouth, swallowing capsules whole without opening, breaking, or chewing them. 1
Dosing Strategy
The standard initial dose is 15 mg/kg once daily, based on actual or ideal body weight (whichever is less). For a 70-kg patient, this equals 1050 mg daily. 1
Dose Calculation
- Standard dosing: 15 mg/kg/day orally once daily
- For 70 kg patient: 15 mg/kg × 70 kg = 1050 mg/day
- Available as 500 mg capsules, so give two capsules (1000 mg) daily as the practical dose
Context-Specific Dosing
For hyperleukocytosis in acute leukemia (WBC >100,000/μL): Use higher doses of 50-60 mg/kg/day until WBC drops below 10-20 × 10⁹/L. 2 This would be 3500-4200 mg/day for a 70-kg patient, continued until cytoreduction is achieved.
For myeloproliferative neoplasms (polycythemia vera, essential thrombocythemia): Target dose is typically 2 g/day (approximately 30 mg/kg for 70 kg), though some protocols use up to 2.5 g/day in patients >80 kg. 3, 4, 5
Administration Instructions
- Swallow capsules whole with water—never open, break, or chew due to cytotoxic risk 1
- Timing: Can be given as single daily dose, optionally at bedtime or with main meal to reduce gastrointestinal side effects 6
- Folic acid prophylaxis is recommended during therapy 1
Dose Adjustments
Renal Impairment
Reduce dose by 50% if creatinine clearance <60 mL/min or end-stage renal disease:
- CrCl ≥60 mL/min: 15 mg/kg/day (1050 mg for 70 kg)
- CrCl <60 mL/min or ESRD: 7.5 mg/kg/day (525 mg for 70 kg)
- On dialysis days: administer after hemodialysis 1
Toxicity-Based Modifications
Monitor CBC weekly initially, then adjust:
- Hold for: ANC <1.0 × 10⁹/L, platelets <100 × 10⁹/L, or hemoglobin <10 g/dL 4
- Discontinue for: Cutaneous vasculitis, leg ulcers, severe mucocutaneous toxicity, or confirmed hemolytic anemia 1
Monitoring Requirements
- Baseline: CBC, renal function, liver enzymes, pregnancy test if applicable 6, 1
- During therapy: CBC weekly until stable dose achieved, then at minimum monthly 6, 1
- Correct severe anemia before starting therapy 1
Clinical Pearls
The drug reaches peak plasma levels in 1-4 hours with excellent oral bioavailability (108%), so IV administration offers no advantage unless oral route is impossible. 7 For emergency cytoreduction in hyperleukocytosis, a single 50-100 mg/kg dose can reduce blast counts by 50% within 24 hours. 8
Common pitfall: Avoid excessive red blood cell transfusions during hyperleukocytosis treatment, as this increases blood viscosity. Implement tumor lysis prophylaxis (hydration, allopurinol/rasburicase) when treating high WBC counts. 2
For myeloproliferative disorders, resistance/intolerance is defined as failure to achieve hematologic control after 3 months at ≥2 g/day, requiring switch to alternative agents like interferon-alpha or ruxolitinib. 3, 4, 5