The action of xanthine oxidase in uric acid synthesis and metabolism of allopurinol. (Modified and reproduced, with permission, from Katzung BG, editor: Basic & Clinical Pharmacology, 11th ed. McGraw-Hill, 2012: Fig. 36–7.) Source: Chapter 36. NSAIDs, Acetaminophen, & Drugs Used in Rheumatoid Arthritis & Gout, Katzung & Trevor's Pharmacology: Examination & Board Review, 10e Citation: Trevor AJ, Katzung BG, Kruidering-Hall MM, Masters SB. Katzung & Trevor's Pharmacology: Examination & Board Review, 10e; 2013 Available at: http://accesspharmacy.mhmedical.com/DownloadImage.aspx?image=/data/books/trev10/trev10_c036f003.png&sec=41820127&BookID=514&ChapterSecID=41817552&imagename= Accessed: November 13, 2017 Copyright © 2017 McGraw-Hill Education. All rights reserved