Challenges of Drug Delivery

This chapter provides an overview of the various physical and chemical challenges encountered in the physiological environment that prevent therapeutics from reaching the site of action. The chapter discusses the concept of dosing maintenance and the therapeutic window. It provides an introduction on how polymer-based carrier systems and polymer conjugates can be used to overcome these barriers. In order to reach the systemic circulation and/or the site of action, all molecules must cross a series of physiological barriers, particularly epithelial, mucacosal, and endothelial membranes. The chapter explains the barriers to drug delivery, and their associated properties. It discusses the effects of drug metabolism on drug absorption, including the use of transport proteins and enzymes to hinder or aid absorption. The route of administration and delivery method, dose and release profile, as well as physiology changes due to pathology play a role in determining the biological effect of a drug molecule.