Functional characteristics of CYP3A4 allelic variants on the metabolism of loperamide in vitro

Abstract

Qian-Meng Lin,1 Ying-Hui Li,1 Qian Liu,1 Ni-Hong Pang,1 Ren-Ai Xu,2 Jian-Ping Cai,3 Guo-Xin Hu1 1School of Pharmaceutical Sciences, Wenzhou Medical University, Wenzhou 325035, People’s Republic of China; 2Department of Pharmacy, The First Affiliated Hospital of Wenzhou Medical University, Wenzhou 325035, People’s Republic of China; 3The Ministry of Health (MOH) Key Laboratory of Geriatrics, Beijing Hospital, National Center of Gerontology, Beijing 100730, People’s Republic of ChinaCorrespondence: Guo-Xin HuSchool of Pharmaceutical Sciences, Wenzhou Medical University, Chashan Street, Chashan Town, Wenzhou 325035, People’s Republic of ChinaEmail [email protected] CaiThe Key Laboratory of Geriatrics, Beijing Hospital, Beijing Institute of Geriatrics, Ministry of Health, Dongdan Dahua Road, Beijing 100730, People’s Republic of ChinaEmail [email protected]: Cytochrome P450 3A4 (CYP3A4) appears to be genetically polymorphic, which in turn contributes to interindividual variability in response to therapeutic drugs. Loperamide, identified as a CYP3A4 substrate, is prone to misuse and abuse and has high risks of life-threatening cardiotoxicity.Methods: Thus, this study is designed to evaluate the enzymatic characteristics of 29 CYP3A4 alleles toward loperamide in vitro, including the 7 novel CYP3A4 variants (*28–*34). The incubation system (containing CYP3A4 enzyme, cytochrome b5, 0.5–20 μM loperamide, potassium phosphate buffer and nicotinamide adenine dinucleotide phosphate) was subject to 40-mins incubation at 37°C and the concentrations of N-demethylated loperamide were quantified by UPLC-MS/MS.Results: As a result, CYP3A4.6, .17, .20 and .30 showed extremely low activity or no activity and the rest of CYP3A4 variants presented varying degrees of decrements in catalytical activities when compared with CYP3A4.1.Conclusion: As the first study to identify the properties of these CYP3A4 variants toward loperamide metabolism, our investigation may establish the genotype–phenotype relationship for loperamide, predict an individual’s capability in response to loperamide, and provide some guidance of clinical medication and treatment for loperamide.Keywords: CYP3A4, genetic polymorphism, interindividual variability, loperamide, misuse and abuse, cardiotoxicity, personalized treatment

Keywords

• CYP3A4
• genetic polymorphism
• interindividual variability
• loperamide
• misuse and abuse
• cardiotoxicity
• personalized treatment