Objective: Previous studies suggest that darbepoetin might stimulate erythropoiesis in preterm neonates more effectively if injected subcutaneously (s.c.) than if infused intravenously (i.v.). It has been postulated that this is because very high plasma concentrations after i.v. dosing result in urinary loss of the drug. However, this theory has not been tested systematically, and no direct comparisons have been made between s.c. and i.v. dosing of darbepoetin in preterm neonates.Study design: Preterm neonates were eligible for this pilot study if they were born at p32 weeks gestation with a weight of p1500 g, and had a hemoglobin p10.5 g/dl. The darbepoetin was given (4 mg/kg) i.v., over 4 h, if an i.v. was already in place and s.c. if no i.v. was in place. Urine was collected for drug quantification before dosing and for 48 h after. Blood was obtained for immature reticulocyte fraction (IRF), absolute reticulocyte count (ARC) and reticulocyte % before and 96 h after dosing.

Infants with Rh hemolytic disease can develop a "late" anemia characterized by low serum concentrations of erythropoietin but erythroid progenitors that remain highly erythropoietin-responsive. Erythropoietin administration was evaluated in two patients as an alternative to transfusion. Reticulocyte counts increased after 5 days of treatment, and hematocrits increased after 10 days. Neither patient received erythrocyte transfusions following erythropoietin therapy.