Therapeutic drug monitoring in neonates is necessary because neonates have very specific pathways of absorption, distribution and elimination of drugs.

The aim of this study was to determine plasma concentrations of the drugs amikacin, gentamicin and phenobarbital to control adequacy of therapy.

A prospective survey was performed in the NICU of the Institute for Neonatology in Belgrade from 2 Feb 2007 to 24 Oct 2007.

213 newborns were observed (130 boys and 83 girls), divided into three groups according to kind of drug they recieved. First group received amikacin (52), second group gentamicin (111), and the third group phenobarbital (50). In the first and the second group drugs were administerd intravenously, and in the third group intravenously and orally. Concentrations of the drugs were determined by fluorescence polarization immunoassay (FPIA), which is a very sensitive method and detects drugs at nmol levels on machines from Abbot and Roche.

The results were analyzed by modern statistic methods:

• Pearson Chi Square test, Mann–Whitney U test, Kruskal-Wallis analysis variance.

• Univariate logistic regression analysis, multivariate logistic regression analysis.

Conclusion Levels of investigated drugs in blood of examined neonates did not depend on sex (χ2 = 2.905; p>0.05); but did depend on length of administration of the drug (χ2 = 12.150; p = 0.002) and body weight of patient (χ2 = 28.934; p<0.001). In the third group, in which drugs were administered intravenously and orally, levels of drugs in blood also depended on method of administration (χ2 = 14.201; p = 0.001).