Principle of ion exchange in drug delivery systems Principle of ion exchange in drug delivery systems. Cation exchangers such as poly(styrene sulfonate) will complex with positively charged drug (D+) and release by exchanging with a cation in the gastrointestinal fluid. Anion exchangers complex with negatively charged (D−) drugs and release by exchanging with anions. Source: Complexation and Protein Binding, Applied Physical Pharmacy, 2e Citation: Amiji MM, Cook TJ, Mobley W. Applied Physical Pharmacy, 2e; 2013 Available at: https://accesspharmacy.mhmedical.com/DownloadImage.aspx?image=/data/Books/993/Amiji_ch7_Fig-07-10.jpeg&sec=62304384&BookID=993&ChapterSecID=62304328&imagename= Accessed: December 28, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved