Mechanisms of Drug Absorption and Excretion Passage of Drugs in and out of the Central Nervous System

Abstract

Within the past few years, there has been a striking expansion of the understanding of the processes which govern the exchange of drugs between blood and the tissues and fluids of the central nervous system.3 The mystical quality of the euphonic blood-brain barrier has been destroyed by well­ planned experiments . A surprising number of previously speculative notions now rest on supporting experimental data. The methodology and concepts developed in the study of ion and drug movement in the kidney and across other biological membranes, have been effectively utilized in the study of the exchanges between blood, cerebrospinal fluid, and brain. The plan of this review is to deal with methodological considerations and then to explore what might be called the pharmacological anatomy of the CNS including the formation and flow of the CSF. Understanding of the newer concepts in these areas is basic to the primary portion of this review which is a consideration of the exchange of compounds between blood, CSF, and brain. A concluding section will explore the implications of the above in a few clinical situations.