Aminoglycoside trough levels in neonates

Abstract

Drug safety depends on trough levels. Objective of the study was to measure gentamicin and amikacin trough levels in neonates and to identify risk groups by gestational and postnatal age. Gentamicin and amikacin were applied according to the clinical practice guidelines. Trough levels (mg/l) were determined using fluorescence polarization immunoassay methodology. Target trough levels were <2 mg/l for gentamicin, and <10 mg/l for amikacin. Patients were divided in 3 groups by gestational age: I < or =32, II 33-36, and III > or =37 gestational weeks and, by postnatal age, in 2 groups: < or =7 and >7 days. Out of 163 neonates, 111 were receiving gentamicin and 52 amikacin. Mean amikacin trough level was 7.8 +/- 4.8 mg/l and, in group 110.5 +/- 4.9 mg/l, which was above the target range and significantly higher than in group II (LSD, p < 0.05). In the amikacin group, 26 patients were 7 and less, and 26 more than 7 days old, without significant differences in trough levels between the groups. In the gentamicin group, 52.3% of neonates had trough values within the target range. Gentamicin trough level in group I was above the trough range, 3.7 +/- 1.8, 2.3 +/- 1.5 in group II and, 1.8 +/- 1.4 mg/l in group III. The difference in trough levels among the groups was highly significant (F = 9.015, p < 0.001, chi2 = 17.576, p < 0.001). Further analysis revealed that differences between groups I and II (LSD, p = 0.002) and between I and III (LSD, p = 0.000) were highly significant. Obtained gentamicin and amikacin trough levels are high. Inverse correlation has been confirmed between trough level and gestational age, with highly significant difference, and the risk group has been identified. There is obviously a need to change the dosing regimen in terms of those with extended intervals, particularly for neonates of the lowest gestational age, along with pharmacokinetic measurements.