“Maximum tolerated dose” vs “fixed low‐dose” hydroxyurea for treatment of adults with sickle cell anemia

Maximum tolerated dose" vs "fixed low-dose" hydroxyurea for treatment of adults with sickle cell anemia To the Editor:Despite evidence that hydroxyurea is effective for sickle cell anemia (SCA), implementation of the "maximum tolerated dose" regimen in adults is poor. 1 We recently reported a study of "fixed low-dose" hydroxyurea (500 mg/day) for adults with SCA in Ibadan, Nigeria. 2 Here we compare the outcomes of "fixed low-dose" hydroxyurea in Nigeria with "maximum tolerated dose" hydroxyurea in the United States and Canada as reported in the Multicenter Study of Hydroxyurea (MSH).3,4 The MSH was the seminal trial conducted in the 1990s that led to FDA approval of hydroxyurea for SCA.Responses to "fixed low-dose" and "maximum tolerated dose" hydroxyurea appear to be similar.We propose that these two regimens be compared in a prospective trial in adults with SCA.Hydroxyurea for SCA increases hemoglobin F and reduces pain crises, acute chest syndrome and blood transfusions.5 The agent is initiated at 15 mg/kg/day in adults followed by dose escalations up to 35 mg/kg/day if tolerated-the "maximum tolerated dose" approach of ORCID