Evaluation of the Impact of Renal Function on the Pharmacokinetics of SIKLOS ® (DARH)

Inclusion Criteria: * Age ≥ 18 years. * Male or female. * Sickle cell disease (SS or S-β0thal) confirmed by haemoglobin electrophoresis and genotyping by deoxyribonucleic acid (DNA) analysis. * Affiliation to a social security system. * Having freely consented in writing after being informed of the objective, programme and potential risks incurred. These criteria will apply to the 3 groups of sickle cell disease patients according to the renal function stage defined by the glomerular filtration rate (GFR) estimated by the formula of the Chronic Kidney Disease EPIdemiology (CKD EPI) collaboration without ethnic criterion during the last 6 months before inclusion: * Normal-renal function: 90 ≤ GFR ≤ 130 mL/min/1.73m2 in women or 140 mL/min/1.73m2 in men. * Moderate renal failure: 30 ≤ GFR ≤ 60 mL/min/1.73m2. * Glomerular renal hyperfiltration: GFR \> 130 mL/min/1.73m2 in women and GFR \> 140 mL/min/1.73m2 in men. * Treated with hydroxyurea (Siklos®) with a stable dosage for at least one week ± 2 days before inclusion in the study and dose administered in the morning at 9:00 ± 15 minutes. Exclusion Criteria: * Refusal to consent. * Patients that do not comply. * Occurrence of vaso-occlusive crisis in the month prior to the inclusion in the study. * Patients having had an exchange transfusion in the 15 days before inclusion in the study. * Patients participating in another clinical trial or in the exclusion period of a previous clinical trial. * Patients treated with a diuretic. * Dialysis patient. * Patients with an intercurrent disorder, especially inflammatory, that has not recovered for at least one month. * Pregnant or breast-feeding women. * Patients deprived of liberty or under legal protection. * Patients who cannot understand the objective and the course of the study, incapable of giving their consent. * In the event of severe hepatic failure. * In the event of severe renal failure (creatinine clearance \< 30 ml/min). * Patients who show toxic signs of bone marrow suppression.