Last reviewed 2026-04-23 · How we verify

Moderate Dose Hydroxyurea

Hydroxyurea inhibits ribonucleotide reductase to reduce DNA synthesis and increase fetal hemoglobin production, thereby reducing sickling and hemolysis.

Hydroxyurea inhibits ribonucleotide reductase to reduce DNA synthesis and increase fetal hemoglobin production, thereby reducing sickling and hemolysis. Used for Sickle cell disease (reduction of vaso-occlusive crises and acute chest syndrome), Polycythemia vera, Essential thrombocythemia.

At a glance

Mechanism of action

Hydroxyurea is a ribonucleotide reductase inhibitor that decreases deoxyribonucleotide pools, slowing DNA replication in rapidly dividing cells. In sickle cell disease, it increases fetal hemoglobin (HbF) expression, which inhibits polymerization of sickle hemoglobin and reduces vaso-occlusive crises. The moderate dose regimen aims to balance efficacy with tolerability.

Approved indications

• Sickle cell disease (reduction of vaso-occlusive crises and acute chest syndrome)
• Polycythemia vera
• Essential thrombocythemia

Common side effects

• Myelosuppression (anemia, leukopenia, thrombocytopenia)
• Macrocytosis
• Nausea and vomiting
• Headache
• Elevated uric acid/hyperuricemia
• Cutaneous reactions

Key clinical trials

• Stroke Prevention in Nigeria 2 Trial (PHASE4)
• Study of Biomarker-Based Treatment of Acute Myeloid Leukemia (PHASE1, PHASE2)
• Stroke Prevention in Young Adults With Sickle Cell Anemia
• De-Escalation Therapy for Human Papillomavirus Negative Disease (PHASE2)
• Optimizing Hydroxyurea Dosage With Pharmakokinetic in Patients Suffering of Moderate to Severe Sickle Cell Anemia (PHASE2, PHASE3)
• Moderate Dose Hydroxyurea for Secondary Stroke Prevention in Children With Sickle Cell Disease in Sub-Saharan Africa (PHASE3)
• Primary Prevention of Stroke in Children With SCD in Sub-Saharan Africa II (PHASE3)

Primary sources

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