Therapeutic drug monitoring--the appropriate use of drug level measurement in the care of the neonate.

Neonates and young infants are in a unique and dynamic pharmacokinetic state, in which they undergo relatively rapid maturational changes in drug absorption, distribution, metabolism, and excretion. In addition to these maturational changes, most drug pharmacokinetic studies in neonates show wide interindividual variability despite similar gestational and postnatal ages. Therapeutic drug monitoring is a necessary tool in the neonatal intensive care unit, despite the relative lack of outcome data. This article discusses therapeutic drug monitoring for several frequently used drugs in neonates.