Dear Editor,

We read with great interest the paper of Dimitrou et al. on the impact of antenatal steroids and fluid balance in very low birth weight infants. The authors nicely documented the impact of prenatal steroids on insensible water loss and on urine output. However, one should be aware that diuresis, glomerular filtration rate and tubular function all are different aspects of renal function. While the authors nicely documented a significant increase in diuresis, they were not able to report on other aspects of renal function.

We recently reported on the interindividual variability of amikacin clearance at birth in a large cohort of preterm neonates (n=205, <24 -30 weeks) on respiratory support and hereby illustrated the impact of gestational age, of birth weight and (negative) of the co-administration of a non-selective cyclo-oxygenase inhibitor while prenatal betamethason administration had no effect on amikacin clearance[1] hereby confirming an earlier report in a more limited cohort of preterm neonates (n=159) with the same clinical characteristics.[2]

As stated by the authors, aminoglycoside clearance reflects glomerular filtration rate. By consequence - at least in our cohort - prenatal betamethasone had no effect on glomerular filtration rate.

Unfortunately, we had to use a retrospective approach in our group of preterm neonates. If the authors by chance collected aminoglycoside samples for therapeutic drug monitoring, they might have the unique opportunity to simultaneously study diuresis and GFR in the same cohort of neonates.

References:

1. Allegaert et al. Br J Clin Pharmacol, online available, ref 2006;61:39-48.

2. Allegaert et al. Paed Perinatal Drug Ther 2005;6:149-154.