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Vol. 27, Issue 7, 763-766, July 1999
Laboratory of Biochemical 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 µM,
Vmax = 0.45 ± 0.03 nmol/min/mg of
protein, and
Vmax/KM = 25.2 ± 4.3 µl/min/mg of protein. At the substrate concentration of 20 µM, 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.
Pharmacology and
Toxicology
Faculty of Pharmaceutical Sciences
Chiba
University,
Chiba, Japan (K.K., T.I., K.C.)
Materials Technology
Research Laboratories
Daiichi Pure Chemicals Co. Ltd.
Ibaraki
(N.S.), Japan
Department of Psychiatry
School of Medicine
Showa University
Tokyo, Japan (Y.Y., K.K.)
Copyright © 1999 by The American Society for Pharmacology and Experimental Therapeutics
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