Premium
Metabolism of citalopram enantiomers in CYP2C19/CYP2D6 phenotyped panels of healthy Swedes
Author(s) -
Herrlin Karin,
YasuiFurukori Norio,
Tybring Gunnel,
Widén Jolanta,
Gustafsson Lars L.,
Bertilsson Leif
Publication year - 2003
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 - 10.1046/j.1365-2125.2003.01874.x
Subject(s) - mephenytoin , cyp2c19 , enantiomer , debrisoquine , medicine , chemistry , pharmacology , cyp2d6 , stereochemistry , metabolism , cytochrome p450
Aims To investigate pharmacokinetics of the enantiomers of citalopram (CT) and its metabolites desmethylcitalopram (DCT) and didesmethylcitalopram (DDCT) in Swedish healthy volunteers in relation to CYP2C19 and CYP2D6 geno‐ and phenotypes. Methods Racemic CT was given for seven days to panels with different genotypes and the following mephenytoin (Me) and debrisoquine (De) hydroxylation phenotypes: EM De /EM Me , PM De /EM Me , EM De /PM Me ( n = 6 in all groups), and one PM De /PM Me subject. Blood sampling was carried out during day 7, and all urine was collected for 12 h after the last dose of CT. Results The AUC of S‐CT was significantly higher in the EM De /PM Me panel compared to the EM De /EM Me and PM De /EM Me panels ( P < 0.05), whereas the AUC of R‐CT did not differ between the panels. Similar differences, although they did not reach statistical significance, were noted for S‐DCT and R‐DCT. The enantiomers of DDCT were not quantifiable in PM De, and there was no difference in DDCT enantiomer concentrations between the other two panels. A PM De /PM Me subject stopped taking CT after five days due to severe adverse effects. Based on two time points, this subject had a very long CT half‐life of 95 h. The value of 1.0 for the S/R ratio of the CT trough in this subject was similar to the mean S/R CT trough ratio of the EM De /PM Me panel, but higher than the S/R CT ratio of the EM De /EM Me panel (0.56; 95% CI 0.49–0.63) and the PM De /EM Me panel (0.44; 95% CI 0.31–0.57). Thus the latter two phenotypes eliminated S‐CT more rapidly via CYP2C19. An adverse effect described as an ‘alcohol hangover’ feeling was reported by one subject from each of the three panels. These individuals had the highest concentrations of both CT enantiomers. Conclusions The AUC of S‐, but not R‐(CT) was found to be significantly higher in PM of mephenytoin compared to EMs, PMs may need a lower dosage of CT.