ABSTRACT
Based on a large use over more than 30 years, in adults and children, Hydroxyurea (HU) has emerged as the primary disease-modifying therapy for sickle cell disease (SCD) with salutary laboratory and clinical effects, including reduction in both mortality and mortality. HU is included in the WHO List of Essential Medicines for the treatment of haemoglobinopathies. The mechanisms of action of HU in SCD are multiple and not completely understood, but fetal haemoglobin (HbF) induction is critical for the inhibition of intracellular sickling. Even though a fixed dose (20 mg/kg) was classically recommended, a HU escalated to maximum tolerated dose (MTD) (max 35 mg/kg) has more relevant impacts. Doses are adjusted according to weight and haematological parameters. Most of the laboratory outcomes of use of HU are the increase of haemoglobin level and HbF and the decrease in leucocyte, neutrophil and reticulocyte counts. HU therapy reduces the incidence of pain events, acute chest syndrome, splenic sequestration, infections, malaria and transfusion death. Few side effects (neutropenia, thrombocytopenia, reticulocytopenia, oligospermia) are described but most of them are transitory
