Purpose: This open-label pilot study was designed (1) to determine the effect of hydroxyurea on the hemoglobin level in children with sickle cell anemia, (2) to evaluate the toxicity of hydroxyurea, and (3) to assess any impact of hydroxyurea on the frequency of vaso-occlusive crises (VOCs).
Patients and methods: Ten children (group 1) with three or more VOCs of the extremities or two or more VOCs of the lungs (acute chest syndrome) in the preceding 12 months, and five children (group 2) with hemoglobin levels less than 70 gm/L were treated with hydroxyurea in doses of 20 to 35 mg/kg per day. The frequency of VOCs before hydroxyurea therapy was compared with the frequency during therapy, and the peak hemoglobin levels during hydroxyurea therapy were compared with the pretreatment values.
Results: One patient in group 1 was removed from the study within 1 month because of nausea. Seven of the remaining nine patients in group 1 had a decrease in the frequency of VOCs. The number of VOCs per patient-year for all 14 patients decreased from 2.5 before hydroxyurea therapy to 0.87 during hydroxyurea therapy, a decrease of 65% (p < 0.00001). Two of five patients in group 2 had an increase in hemoglobin of 27 gm/L and 34 gm/L over the baseline. The median rise in hemoglobin was 19 gm/L (range, 7 to 37) for all 14 patients. Nine patients are still receiving hydroxyurea for a median period of 23 months (range, 18 to 59).
Conclusions: Hydroxyurea decreases the severity of anemia in some patients, and it may decrease the frequency of VOC. Its short-term hematologic toxicity is minimal.