Alternative Dosing And Prevention of Transfusions (ADAPT)

All participants will receive an individualized PK hydroxyurea assessment. Participants for whom the PK-process successfully generates a dose in the predicted treatment range of 15-35 mg/kg/day, will start on that personalized dose. Participants for whom the process does not generate a starting hydroxyurea dose in the predicted treatment range, due to potential pitfalls in lab draws, serum storage, sample processing, or hydroxyurea analysis, will start at a default dose of 20.0 ± 2.5 mg/kg/day. For all participants, the hydroxyurea dose will be adjusted as needed based on blood counts to establish the optimal dose. Where necessary, a weekly dosing average will be determined, so that treatment can occur solely with locally available and affordable 500mg hydroxyurea capsules.