RT Journal Article SR Electronic T1 Physiology of the Neonatal Gastrointestinal System Relevant to the Disposition of Orally Administered Medications JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 296 OP 313 DO 10.1124/dmd.118.084418 VO 47 IS 3 A1 April Neal-Kluever A1 Jeffrey Fisher A1 Lawrence Grylack A1 Satoko Kakiuchi-Kiyota A1 Wendy Halpern YR 2019 UL http://dmd.aspetjournals.org/content/47/3/296.abstract AB A thorough knowledge of the newborn (age, birth to 1 month postpartum) infant’s gastrointestinal tract (GIT) is critical to the evaluation of the absorption, distribution, metabolism, and excretion (ADME) of orally administered drugs in this population. Developmental changes in the GIT during the newborn period are important for nutrient uptake as well as the disposition of orally administered medications. Some aspects of gastrointestinal function do not mature until driven by increased dietary complexity and nutritional demands later in the postnatal period. The functionalities present at birth, and subsequent maturation, can also impact the ADME parameters of orally administered compounds. This review will examine some specific contributors to the ADME processes in human neonates, as well as what is currently understood about the drivers for their maturation. Key species differences will be highlighted, with a focus on laboratory animals used in juvenile toxicity studies. Because of the gaps and inconsistencies in our knowledge, we will also highlight areas where additional study is warranted to better inform the appropriate use of medicines specifically intended for neonates.