Granulocyte colony-stimulating factor serum and urine concentrations in neutropenic neonates before and after intravenous administration of recombinant granulocyte colony-stimulating factor
Da. Calhoun et al., Granulocyte colony-stimulating factor serum and urine concentrations in neutropenic neonates before and after intravenous administration of recombinant granulocyte colony-stimulating factor, PEDIATRICS, 105(2), 2000, pp. 392-397
Background. Recombinant granulocyte colony-stimulating factor (rG-CSF) has
been suggested as a treatment for certain varieties of neonatal neutropenia
, but little is known about the pharmacologic disposition of rG-CSF in that
population.
Methods. Ten neutropenic neonates were treated with rG-CSF, 10 mg/kg intrav
enously once daily for 3 to 5 days. Serum and urine samples were obtained b
efore rG-CSF dosing and at intervals thereafter for G-CSF quantification by
enzyme-linked immunosorbent assay.
Results. Five of the neutropenic neonates (termed group 1) were not infecte
d but likely had hyporegenerative neutropenia (4 were born after pregnancy-
induced hypertension/intrauterine growth restriction, and 1 had Rh hemolyti
c disease). Five other infants (group 2) had neutropenia accompanying bacte
rial sepsis and shock. Before receiving the first dose of rG-CSF, endogenou
s G-CSF serum and urine concentrations were relatively low in group 1, aver
aging 130 pg/mL (range: 48-209) in serum and 53 pg/mL (range: 15-141) in ur
ine. Serum concentrations immediately before the final dose were much highe
r (range: 81-24 835 pg/mL), whereas urine concentrations were unchanged (ra
nge: <7 pg/mL-126 pg/mL). In group 2 patients, before receiving the first-d
ose of rG-CSF, endogenous concentrations were very high, averaging 59 575 p
g/mL (range: 20 028-98 280) in serum and 3189 pg/mL (range: 23-4770) in uri
ne. Predose serum concentrations before the final dose (range: 427-14 460 p
g/mL) were lower than before the first dose. The area under the concentrati
on curve after the first dose of rG-CSF administration in group 1 was signi
ficantly lower than after the first dose in group 2, but no difference in a
rea under the concentration curve was observed between groups 1 and 2 after
the last dose of rG-CSF.
Speculation. The principal means of clearing G-CSF from the serum is by sat
urable binding to specific G-CSF receptors (G-CSF-Rs). Therefore, the very
high G-CSF serum and urine concentrations of group 2 patients before the fi
rst rG-CSF dose implies that their G-CSF-Rs were saturated before the dose
was given. We speculate that if G-CSF-Rs are saturated with endogenous G-CS
F, treatment with rG-CSF will add little or nothing to the neonates with se
ptic shock and neutropenia are unlikely to derive benefit from rG-CSF admin
istration.