Therapeutic drug monitoring principles in the neonate. National Academy of CLinical Biochemistry

Therapeutic drug monitoring in the newborn infant is necessary because dose requirements differ greatly from those for older children. These differences stem from major changes in kinetic disposition at the absorption, distribution, and elimination phases. The small blood volume of neonates makes them sensitive to iatrogenic blood loss. Similarly, the small size of these patients means that medication errors frequently lead to morbidity and even mortality. The clinical laboratory must set up strict, high-standard, carefully updated guidelines to ensure the safety of infants who need drug therapy at this very vulnerable phase of their lives.

Published by Clinical chemistry, 1997. The guideline itself is at the source linked here.

pubmed.ncbi.nlm.nih.gov/8990257/