<qa>  What is the second issue that relates to the ability of newborn infants to catalyThis proposal has its origins in a larger initiative to elucidate the pharmacological basis for the interindividual differences observed in opioid responsiveness. Gaps in our knowledge related to opioid disposition in newborns need to be addressed to complete the design of the required overarching initiative in which age could be treated as a continuous variable within a context of PK, PD and PG determinants.This proposal is designed to generate preliminary data that addresses two issues. First, can newborns absorb enterally administered codeine and is this ability determined by PCA or PNA age? The second relates to the ability of newborn infants to catalyze those reactions required to metabolically activate both codeine and morphine. The latter will also be evaluated within the context of PCA versus PNA age. 