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P-glycoprotein in the Developing Human Brain: A Review of the Effects of Ontogeny on the Safety of Opioids in Neonates

Lam, Jessica BSc*,†; Koren, Gideon MD*,†,‡

doi: 10.1097/FTD.0000000000000087
Review Article

Abstract: The human blood brain barrier is responsible for maintaining brain homeostasis and protecting against potentially toxic substances. The ATP-binding cassette drug efflux protein, P-glycoprotein (P-gp) is a key player in actively extruding a wide range of xenobiotics such as opioids from the brain. Because the blood brain barrier is structurally and functionally immature in neonates, opioids may have a greater penetration to the central nervous system. This may influence the efficacy and safety of opioids in the newborn. Understanding the extent of P-gp's expression in the brain in the embryo, fetus, and newborn will facilitate rational opioid use during pregnancy and the neonatal period. This review aims to summarize the current evidence that associates the ontogeny of P-gp and the susceptibility to opioid-induced adverse respiratory effects in neonates. To date, evidence suggests that the expression of P-gp in the human brain is low at birth, contributing to increased susceptibility.

*Department of Pharmacology and Toxicology, University of Toronto;

Division of Clinical Pharmacology and Toxicology, Hospital for Sick Children, Toronto; and

Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Canada.

Correspondence: Gideon Koren, MD, Division of Clinical Pharmacology and Toxicology, Hospital for Sick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8 (e-mail:

The authors have no conflict of interest to declare.

Received October 22, 2013

Accepted December 29, 2013

© 2014 by Lippincott Williams & Wilkins