II. Mechanism: Sickle Cell Anemia
- Increases production of fetal Hemoglobin (HbF) which does not sickle
III. Indications
- Malignancy
- Polycythemia Vera
- First-line agent indicated in high risk disease (history of thrombosis or age over 60 years old)
- Chronic myelocytic Leukemia
- Head and Neck Squamous Cell Cancer
- Melanoma
- Polycythemia Vera
-
Sickle Cell Anemia
- Indications in adults
- Sickle Cell Crisis 3 or more times in 12 months
- Severe or recurrent Acute Chest Syndrome
- Severe symptomatic chronic Anemia affecting functional status
- Sickle cell associated pain significantly impacting function or quality of life
- Indications in children over age 9 months
- All children over age 9 months should be offered Hydroxyurea to reduce complications
- Indications in adults
IV. Adverse Effects
- Anemia
- Neutropenia
- Oral Ulcers
- Skin Ulcers
- Hyperpigmentation
- Leukemogenicity risk in Polycythemia Vera (Exercise caution in age under 40 years old)
- Leukemic transformation 0.4% persons per year
- Myelofibrosis 5% at five years, 33.7% at 10 years
- Ferrari (2019) Hematologica 104(12): 2391-9 [PubMed]
V. Contraindications
- Pregnancy
- Lactation
VI. Monitoring: Sickle Cell Anemia
- Baseline
- Complete Blood Count with differential
- Reticulocyte Count
- Hemoglobin F quantitative measurement
- Comprehensive metabolic panel (Renal Function tests, Liver Function Tests)
- Pregnancy Test
- Labs while adjusting dose (every 4 weeks or more)
- Reticulocyte Count
- Complete Blood Count with differential and Platelets
- Maintain Absolute Neutrophil Count (ANC) > 2,000/mm3
- Maintain Platelet Count >80,000/mm3
- Labs when cytopenia occurs (every 1 week)
- Reticulocyte Count
- Complete Blood Count with differential and Platelets
- Periodic labs when on stable dose (every 2-3 months)
- Reticulocyte Count
- Complete Blood Count with differential and Platelets
- Hemoglobin F quantitative measurement may be obtained to evaluate for response
VII. Management: Sickle Cell Anemia
- Often managed in conjunction with Sickle Cell Disease specialist
- Trial for minimum of 6 months before assessing efficacy
- Encourage compliance for maximal effect
- Starting Doses
- Obtain baseline labs as above prior to initiating Hydroxyurea
- Arrange reliable Contraception for while on Hydroxyurea
- Dosing: Infants and Children
- Hydroxyurea 20 mg/kg daily
- Dosing: Adults with normal Renal Function
- Hydroxyurea 15 mg/kg (round up to nearest 500 mg) daily
- Dosing: Adults with Chronic Kidney Disease
- Hydroxyurea 5-10 mg/kg daily
- Adjusting dose
- See lab monitoring as above
- Maximum daily dose: 35 mg/kg/day
- Decreasing dose
- Indications
- Neutropenia (ANC <2000/mm3)
- Thrombocytopenia (Platelet Count <80,000/mm3)
- Approach
- Consult with specialist
- In some infants and children, ANC >1250/mm3 (instead of 2000/mm3) may be acceptable
- Increase lab monitoring to weekly as above
- Reduce Hydroxyurea dose by 5 mg/kg/day
- Indications
- Increasing dose
- Target ANC 2000 to 4000/mm3
- Increase by 5 mg/kg/day increments every 8 weeks
VIII. Efficacy: Sickle Cell Anemia
- Full benefits may not be seen for the first 6 months after starting Hydroxyurea
- Reduces Sickle Cell Anemia mortality and hospitalizations (fewer episodes of crisis and Acute Chest Syndrome)
- Reduces Sickle Cell Crisis by 50%
- Steinberg (2003) JAMA 289:1645-51 [PubMed]
IX. Resources
- NIH: NHLBI Evidence-Based Management of Sickle Cell Disease: Expert Panel Report, 2014
X. References
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