title: Drug-drug interactions in the metabolism of imidafenacin: role of the human cytochrome P450 enzymes and UDP-glucuronic acid transferases, and potential of imidafenacin to inhibit human cytochrome P450 enzymes.
abstract: Imidafenacin (IM), 4-(2-methyl-1H-imidazol-1-yl)-2,2-diphenylbutanamide, is a newly synthesized antimuscarinic drug developed for the treatment of overactive bladder. To predict clinically relevant drug interactions in the metabolism of IM, the paper investigated: (1) the major enzymes responsible for the metabolism of IM, (2) the effects of concomitant drugs on the inhibition of metabolism of IM, and (3) the effects of IM and its metabolites on the inhibition of human cytochrome P450 (CYP). The elimination of IM and production of oxidative metabolites were mainly catalysed by recombinant CYP3A4, and the elimination of IM by human liver microsomes (HLM) was markedly inhibited by co-incubation with ketoconazole. The production of the N-glucuronide metabolite was only catalysed by recombinant UGT1A4. Clinically established CYP3A4 inhibitors including itraconazole, ketoconazole, erythromycin and clarithromycin inhibited the elimination of IM in HLM. IM and its major metabolites did not affect the activities of CYP enzymes in vitro. The results suggest that the major enzymes responsible for the metabolism of IM are CYP3A4 and UGT1A4, and oxidative metabolism of IM is reduced by concomitant administration of CYP3A4 inhibitors. In contrast, IM and its metabolites have no inhibitory effect on the CYP-mediated metabolism of concomitant drugs.
authors.affiliation: Kyorin Pharmaceutical Co. Ltd, Research Center, Nogi-machi, Shimotsuga-gun, Japan. norihiro.kanayama@mb.kyorin-pharm.co.jp
authors.forename: N
authors.initials: N
authors.lastname: Kanayama
authors.forename: C
authors.initials: C
authors.lastname: Kanari
authors.forename: Y
authors.initials: Y
authors.lastname: Masuda
authors.forename: S
authors.initials: S
authors.lastname: Ohmori
authors.forename: T
authors.initials: T
authors.lastname: Ooie
mesh_terms: D051544:Cytochrome P-450 CYP3A; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D014453:Glucuronosyltransferase / Q000378:metabolism*; D006801:Humans; D007093:Imidazoles / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D066298:In Vitro Techniques; D007583:Jejunum / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D018727:Muscarinic Antagonists / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D007093:Imidazoles; D018727:Muscarinic Antagonists; D011994:Recombinant Proteins; C019787:bilirubin glucuronoside glucuronosyltransferase; D003577:Cytochrome P-450 Enzyme System; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D014453:Glucuronosyltransferase; C120953:imidafenacin