Only one randomized trial, the Multicenter Study of Hydroxyurea for Sickle Cell Anemia (MSH Study), tested the efficacy of hydroxyurea in adults with sickle cell anemia, with six additional analyses either based on this trial or on followup studies. The significant hematological effects of hydroxyurea after 2 years (as compared to the placebo arm) included a small mean increase of g/dl in total hemoglobin and a moderate absolute increase in fetal hemoglobin of percent. The median number of painful crises was 44 percent lower, and the time to the first painful crisis was 3 months, as compared.
