The frequency of pain crises was reported as an outcome in five pediatric studies, with a reduction in frequency reported in three. In one retrospective cohort study in a resource-poor environment, the frequency of pain crises declined from a median of 3 per year to a median of per year during treatment, with a median followup time of 24 months. Of note is the fact that these results were obtained using a fixed dose of hydroxyurea (15 mg/kg/day). A small, high- quality prospective study found a decrease in pain events, from per year in the year prior to.
