Drug Metabolism in the Human Fetus and Newborn Infant

Abstract

This is a literature review designed to present the current state of knowledge regarding drug metabolism in the human fetus. Since pharmaco-kinetic processes, i.e., absorption, distribution, metabolism, and excretion of drugs, largely determine the intensity and duration of drug action, such knowledge is useful as a guideline for drug therapy in the newborn period. Both in vitro and in vivo studies dealing with pre-and postnatal drug metabolism in humans and animal species are reviewed. The liver is considered the principle organ of drug metabolism. Animal fetuses seem to have a negligible capacity to oxidize and conjugate drugs. After birth the capacity increases at different rates, depending on the species, the type of reaction, and the type of drug. There is, on the other hand, evidence that drug metabolism occurs in human fetuses. The human fetal liver contains the drug-metabolizing enzyme system early in gestation. The data which argues for and that arguing against the concept of low drug-oxidizing capacity in the newborn is summarized. The old concepts regarding drug metabolism during the early part of life need reevaluation.