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The role of cytochrome P4502D6 in the metabolism of paroxetine by human liver microsomes.
Author(s) -
Bloomer JC,
Woods FR,
Haddock RE,
Lennard MS,
Tucker GT
Publication year - 1992
Publication title -
british journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.216
H-Index - 146
eISSN - 1365-2125
pISSN - 0306-5251
DOI - 10.1111/j.1365-2125.1992.tb04082.x
Subject(s) - microsome , paroxetine , debrisoquine , quinidine , cytochrome p450 , pharmacology , chemistry , metabolism , cyp3a4 , enzyme , biochemistry , biology , cyp2d6 , serotonin , receptor
Paroxetine is a selective serotonin reuptake inhibitor possessing anti‐ depressant activity. Demethylenation of the methylenedioxy phenyl group is the initial step in its metabolism, the liberated carbon appearing in vitro as formate. A radioassay involving [14C‐methylenedioxy] paroxetine was developed and used to examine the role of cytochrome P4502D6 in paroxetine metabolism by human liver microsomes. The rate of formate production was much higher in microsomes from an extensive metaboliser of debrisoquine than from a poor metaboliser. Also, demethylenation of paroxetine was inhibited by the quinidine and quinine isomer pair in microsomes from the extensive metaboliser only. These observations strongly suggested that the process was catalysed by the enzyme cytochrome P4502D6. Metabolism could not be completely inhibited by quinidine, the residual activity representing the contribution of at least one other enzyme. The ability of microsomes from a poor metaboliser of debrisoquine to demethylenate paroxetine provided further evidence for the involvement of an enzyme distinct from P4502D6. This was confirmed by kinetic analysis of the process in microsomes from both poor and extensive metabolisers. It is concluded that, in man, the initial step of paroxetine metabolism is performed by at least two enzymes, one of which is cytochrome P4502D6.