title: Sertraline N-demethylation is catalyzed by multiple isoforms of human cytochrome P-450 in vitro.
abstract: Sertraline, a new antidepressant of the selective serotonin reuptake inhibitor class, is extensively metabolized to desmethylsertraline in humans. We identified the cytochrome P-450 (CYP) isoforms involved in sertraline N-demethylation using pooled human liver microsomes and cDNA-expressed CYP isoforms. Eadie-Hofstee plots for the sertraline N-demethylation in human liver microsomes were monophasic. The estimated Michaelis-Menten kinetic parameters were: KM = 18.1 +/- 2.0 microM, Vmax = 0.45 +/- 0.03 nmol/min/mg of protein, and Vmax/KM = 25.2 +/- 4.3 microl/min/mg of protein. At the substrate concentration of 20 microM, which approximated the apparent KM value, sulfaphenazole (CYP2C9 inhibitor) and triazolam (CYP3A substrate) reduced the N-demethylation activities by 20 to 35% in human liver microsomes, whereas the inhibition induced by mephenytoin (CYP2C19 substrate) or quinidine (CYP2D6 inhibitor) was marginal. The anti-CYP2B6 antibody inhibited the sertraline N-demethylation activities by 35%. Sertraline N-demethylation activities were detected in all cDNA-expressed CYP isoforms studied. In particular, CYP2C19, CYP2B6, CYP2C9-Arg, CYP2D6-Val, and CYP3A4 all showed relatively high activity. When the contributions of CYP2D6, CYP2C9, CYP2B6, CYP2C19, and CYP3A4 were estimated from the Vmax/KM of cDNA-expressed CYP isoforms and from their contents in pooled human liver microsomes, the values were found to be 35, 29, 14, 13, and 9%, respectively. The results suggest that at least five isoforms of CYP (CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP3A4) are involved in the sertraline N-demethylation in human liver microsomes and that the contribution of any individual isoform does not exceed 40% of overall metabolism. Therefore, concurrent administration of a drug that inhibits a specific CYP isoform is unlikely to cause a marked increase in the plasma concentration of sertraline.
authors.affiliation: Laboratory of Biochemical Pharmacology and Toxicology Faculty of Pharmaceutical Sciences Chiba University, Chiba, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Kobayashi
authors.forename: T
authors.initials: T
authors.lastname: Ishizuka
authors.forename: N
authors.initials: N
authors.lastname: Shimada
authors.forename: Y
authors.initials: Y
authors.lastname: Yoshimura
authors.forename: K
authors.initials: K
authors.lastname: Kamijima
authors.forename: K
authors.initials: K
authors.lastname: Chiba
mesh_terms: D000928:Antidepressive Agents / Q000493:pharmacokinetics*; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism*; D008745:Methylation; D008862:Microsomes, Liver / Q000201:enzymology; D011994:Recombinant Proteins / Q000378:metabolism; D017367:Selective Serotonin Reuptake Inhibitors / Q000493:pharmacokinetics*; D020280:Sertraline / Q000493:pharmacokinetics*
chemical_list: D000928:Antidepressive Agents; D003577:Cytochrome P-450 Enzyme System; D007527:Isoenzymes; D011994:Recombinant Proteins; D017367:Selective Serotonin Reuptake Inhibitors; D020280:Sertraline