Heart rate variability as an indicator for morphine pharmacokinetics and pharmacodynamics in critically ill newborn infants.

Morphine is the commonest drug used for analgesia in newborn infants. It is a natural opioid that acts as an agonist at the mu and kappa receptors, which are receptors for analgesia and sedation. Morphine pharmacokinetics and pharmacodynamics (PKPD) for the newborn infant population are not well understood. The objective of this study is to use morphine PKPD parameters to estimate morphine plasma concentrations to be correlated with heart rate variability in the neonatal population.