Review ArticleSignificance of Ethnic Factors in Immunosuppressive Therapy Management After Organ TransplantationYamada, Takaaki PhD*; Zhang, Mengyu BS†; Masuda, Satohiro PhD*,†,‡,§Author Information *Department of Pharmacy, Kyushu University Hospital; †Department of Clinical Pharmacology and Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan; ‡Department of Pharmacy, International University of Health and Welfare Narita Hospital, Chiba, Japan; and §Department of Clinical Pharmacy, Faculty of Pharmaceutical Sciences, International University of Health and Welfare, Tokyo, Japan. Correspondence: Satohiro Masuda, PhD, Department of Clinical Pharmacy, Faculty of Pharmaceutical Sciences, International University of Health and Welfare Narita Hospital, 1-24-1 Minami-Aoyama, Minato-ku, Tokyo 107-0062, Japan (e-mail: email@example.com). Supported in part by Grant-in-Aid for Scientific Research (KAKENHI) from the Ministry of Education, Science, Culture, Sports, and Technology of Japan (MEXT) (Grant numbers: 18H02588 to S. Masuda, 18K14951 to T. Yamada). The authors declare no conflict of interest. Received November 18, 2019 Accepted January 24, 2020 Therapeutic Drug Monitoring: June 2020 - Volume 42 - Issue 3 - p 369-380 doi: 10.1097/FTD.0000000000000748 Buy Metrics Abstract Clinical outcomes after organ transplantation have greatly improved in the past 2 decades with the discovery and development of immunosuppressive drugs such as calcineurin inhibitors, antiproliferative agents, and mammalian target of rapamycin inhibitors. However, individualized dosage regimens have not yet been fully established for these drugs except for therapeutic drug monitoring-based dosage modification because of extensive interindividual variations in immunosuppressive drug pharmacokinetics. The variations in immunosuppressive drug pharmacokinetics are attributed to interindividual variations in the functional activity of cytochrome P450 enzymes, UDP-glucuronosyltransferases, and ATP-binding cassette subfamily B member 1 (known as P-glycoprotein or multidrug resistance 1) in the liver and small intestine. Some genetic variations have been found to be involved to at least some degree in pharmacokinetic variations in post-transplant immunosuppressive therapy. It is well known that the frequencies and effect size of minor alleles vary greatly between different races. Thus, ethnic considerations might provide useful information for optimizing individualized immunosuppressive therapy after organ transplantation. Here, we review ethnic factors affecting the pharmacokinetics of immunosuppressive drugs requiring therapeutic drug monitoring, including tacrolimus, cyclosporine, mycophenolate mofetil, sirolimus, and everolimus. Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.