Hydroxyurea therapy associated with declining serum levels of magnesium in children with sickle cell anemia

Objective: To obtain quantitative serum levels of total and ionized magnesium (Mg 2+ ) in children with homozygous sickle cell anemia (SCA) undergoing therapy with hydroxyurea. Study design: Five children, ages 11 to 14 years with homozygous SCA, were enrolled in a dose-escalating trial of hydroxyurea over an 18-month period. Serum levels of total and ionized magnesium together with ionized K + , Na + , and Ca 2+ were measured before hydroxyurea and every 6 months during hydroxyurea therapy. Results: Before treatment, 4 of the 5 patients had low or below-normal serum concentrations of Mg 2+ (normal range, 0.51-0.67 mmol/L). All 5 became Mg 2+ -deficient during hydroxyurea therapy, with no indication of recovery until after 12 to 18 months of drug administration ( P + , Na + , and Ca 2+ remained consistently within normal ranges. Conclusions: These findings warrant a controlled study of the effects of magnesium supplementation in patients with SCA receiving hydroxyurea. Potentially, such therapy could alleviate or prevent vaso-occlusive crises. (J Pediatr 2002;140:565-9)