The pharmacology of anaesthetics in the neonate.

Neonatal anaesthesia dosing needs to be based on physiological characteristics of the newborn, pharmacokinetic/pharmacodynamic considerations and the adverse effects profile. Disease processes and treatments in this group are distinct from adults. Absorption, distribution and clearance are altered because of immaturity of enzyme, anatomical or physiological systems resulting in extensive variability of drug disposition in neonates. This is further compounded by pharmacogenomic influences. Population and physiological-based pharmacokinetic modelling have improved understanding of maturation and subsequent dose approximation. Postmenstrual age is a reasonable measure for maturation, although postnatal age may also have an impact. The neonatal response to drugs is also altered. Although neuromuscular monitoring is robust, there remains a need for other clinically applicable tools to assess pharmacodynamics that can provide effect feedback. In neonatal anaesthesia, a specific focus of interest is tools to assess depth of anaesthesia, sedation and pain. These tools have potential to improve effectiveness and safety.