Development of a method to measure methadone enantiomers and its metabolites without enantiomer standard compounds for the plasma of methadone maintenance patients.
A liquid chromatography-photodiode array (LC-PDA) method using a chiral analytical column was developed to determine the plasma levels of enantiomers of methadone and its chiral metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), without the standard compounds of R-form or S-form enantiomers. This method was established by the characteristics of recombinant cytochrome P-450 (CYP) isozymes, where CYP2C19 prefers to metabolize R-methadone and CYP2B6 prefers to metabolize S-methadone. We incubated the racemic methadone standard with either enzyme for 24 h. We identified the retention times of R- and S-methadone to be around 10.72 and 14.46 min, respectively. Furthermore, we determined the retention times of R- and S-EDDP to be approximately 6.76 and 7.72 min, respectively. No interferences were shown through the retention times of morphine, buprenorphine and diazepam. With the high recovery rate of a solid-phase extraction procedure, this method was applied in analyzing plasma concentrations of seven methadone maintenance patients where R- and S-methadone and R- and S-EDDP were 233.4 +/- 154.9 and 185.9 +/- 136.3 ng/mL and 84.4 +/- 99.4 and 37.6 +/- 22.9 ng/mL, respectively. These data suggest that the present method can be applied for routine assay for plasma methadone and EDDP concentrations for patients under treatment.
Wang
Sheng-Chang
SC
Division of Mental Health and Addiction Medicine, Institute of Population Health Sciences, National Health Research Institutes, 35 Keyan Road, Zhunan, Miaoli County 350, Taiwan.
Ho
Ing-Kang
IK
Wu
Shiow-Ling
SL
Liu
Shu Chih
SC
Kuo
Hsiang-Wei
HW
Lin
Keh-Ming
KM
Liu
Yu-Li
YL
D000328:Adult; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism*; D002853:Chromatography, Liquid / Q000379:methods*; D065702:Cytochrome P-450 CYP2B6; D065731:Cytochrome P-450 CYP2C19; D006556:Heroin Dependence / Q000097:blood / Q000188:drug therapy* / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D008297:Male; D008691:Methadone / Q000097:blood / Q000737:chemistry* / Q000378:metabolism / Q000627:therapeutic use; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism*; D013237:Stereoisomerism
D001189:Aryl Hydrocarbon Hydroxylases; C585599:CYP2B6 protein, human; C045793:CYP2C19 protein, human; D065702:Cytochrome P-450 CYP2B6; D065731:Cytochrome P-450 CYP2C19; D010089:Oxidoreductases, N-Demethylating; D008691:Methadone