Impact of polymorphisms of cytochrome-P450 isoenzymes 2C9, 2C19 and 2D6 on plasma concentrations and clinical effects of antidepressants in a naturalistic clinical setting.
OBJECTIVE
This evaluation focuses on polymorphisms of the cytochrome-P450 (CYP) isoenzymes 2C9, 2C19 and 2D6 and their association with plasma concentrations within a typical clinical setting. Side effects and treatment response were analysed in an exploratory approach in poor and ultra-rapid metabolisers.


METHODS
We analysed 136 Caucasian depressed inpatients treated with amitriptyline, citalopram, clomipramine, doxepin, fluvoxamine, mirtazapine, paroxetine, sertraline and venlafaxine, who underwent weekly plasma concentration measurements, assessment of the severity of illness and side effects during their stay in the hospital. Patients were genotyped with respect to CYP2C9 alleles *1 and *2, the CYP2C19 alleles *1, *2 and *3 and the CYP2D6 alleles *1 to *9 and CYP2D6 gene duplication.


RESULTS
CYP2D6 poor metaboliser genotype and co-medication with inhibitors of CYP2D6 were associated with higher plasma concentrations than the drug-specific median plasma concentration when normalised to dose; plasma concentrations of CYP2C19 extensive metabolisers and smokers were significantly lower than the drug-specific median. Five of the six CYP2D6 poor metabolisers experienced side effects. Response was not associated with plasma concentrations above or below the lower limit of a presumed therapeutic range.


CONCLUSIONS
These data indicate a significant influence of the CYP2D6 genotype, minor influence of the CYP2C19 genotype and no influence of the CYP2C9 genotype on plasma concentrations of patients taking mainly second-generation antidepressants. Because of the good tolerability of the latter and the flat dose-response relationship, genotyping should only be considered in cases of suspected side effects.
Grasmäder
Katja
K
Department of Psychiatry, University of Bonn, Sigmund-Freud-Strasse 25, 53105 Bonn, Germany.
Verwohlt
Petra Louise
PL
Rietschel
Marcella
M
Dragicevic
Aleksandra
A
Müller
Matthias
M
Hiemke
Christoph
C
Freymann
Nikolaus
N
Zobel
Astrid
A
Maier
Wolfgang
W
Rao
Marie Luise
ML
D000928:Antidepressive Agents / Q000097:blood / Q000627:therapeutic use*; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D003866:Depressive Disorder / Q000097:blood / Q000145:classification / Q000188:drug therapy*; D005260:Female; D005838:Genotype; D006801:Humans; D007527:Isoenzymes / Q000235:genetics; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010597:Pharmacogenetics; D011110:Polymorphism, Genetic; D012720:Severity of Illness Index
D000928:Antidepressive Agents; D007527:Isoenzymes; D003577:Cytochrome P-450 Enzyme System