Pain perception development and maturation.

Newborn infants are not small adults. The pharmacokinetics and dynamics of analgesic drugs are immature at birth. Volumes of distribution, drug clearances, side-effects and drug efficacy all differ in newborns as compared to adults. Interestingly, these parameters develop before birth and during the postnatal period, reaching adult values after a period of months or years. This means that clinicians should anticipate on pharmacokinetic/pharmacodynamic (PK/PD) changes in newborns with increasing post-conceptual age. The ability to perceive pain might also be immature at birth. Lower pain thresholds due to the absence of inhibitory descending spinothalamic fibers and a not yet fully developed cortical pain memory system are points of interest for our understanding of differences in pain perception in the newborn infant. Although this is a relatively unexplored area of research in humans, we will discuss the maturation and development of neonatal pain experience and perception in this paper.