Long Term Effects of Hydroxyurea Therapy in Children With Sickle Cell Disease

The primary objectives of this prospective, observational study are (1) to describe the long-term cellular, molecular, and clinical effects of hydroxyurea therapy in sickle cell disease, and (2) to perform hydroxyurea pharmacokinetics studies. This study will follow sickle cell patients being treated with hydroxyurea for a long period of time to evaluate the long-term cellular and molecular effects of the drug on the patients' body. This study will consist of two patient groups. One group will be made up of patients who have received hydroxyurea therapy before entering the study. The second group will be made up of patients who have not received hydroxyurea before study entry.