Drug Distribution

Abstract

Once in systemic circulation, the drug will (reversibly) extravasate to other tissues, including the targeted organ/s, a process that we will refer as drug distribution. Pharmacologically speaking, drug distribution is a critical process, since it will determine (a) the quantity of drug present at its site of action at a given time point and (b) the quantity of drug that reaches other tissues different from the site of action. The pattern of drug distribution will also influence the elimination half-life of drugs and, therefore, the extent of their action. The extent and rate of drug distribution depend on several factors such as the physicochemical properties, vascular permeability, regional blood flow, cardiac output, the ability of the drug to bind plasma proteins and tissue elements, and pH partition. Besides discussing most of such factors, this chapter will briefly present the concepts of real and apparent volumes of distribution.