A high-throughput assay using liquid chromatography-tandem mass spectrometry for simultaneous in vivo phenotyping of 5 major cytochrome p450 enzymes in patients.
The phenotyping cocktail is a practical approach for phenotyping of cytochrome P450 (CYP) enzymes in vivo. In this study, a liquid chromatography-tandem mass spectrometry method using a dual-extraction approach was developed and validated to quantify 5 selective substrates and their metabolites for the simultaneous phenotyping CYPs 1A2, 2C19, 2C9, 2D6, and 3A4 in patient blood samples. The assay was applied in a pilot study of 11 patients with schizophrenia. Five blood samples were collected before and at 1, 2, 4, and 6 hours after administration of a phenotyping cocktail consisting of 100 mg caffeine, 20 mg omeprazole, 25 mg losartan, 30 mg dextromethorphan, and 2 mg midazolam. The method successfully quantitated the CYP enzyme activities without serious side effects in patients. The ratios of metabolite to parent area under the concentration-time curve values were calculated over the 6-hour postdosage to reflect CYP2D6, CYP3A4, and CYP2C9 activities. The ratios of metabolite to parent plasma concentrations were calculated at 4-hour postdosage for CYP1A2 and at 4- or 6-hour postdose for CYP2C19, respectively. The plasma concentration of midazolam at 4 hours was also estimated as another phenotyping index for CYP3A4 activity. The simultaneous assay of all these analytes in a single matrix (plasma) will increase the feasibility of CYP phenotyping in patients.
Ghassabian
Sussan
S
Faculty of Pharmacy, University of Sydney, Camperdown, New South Wales, Australia.
Chetty
Manoranjenni
M
Tattam
Bruce N
BN
Chem
Mraci C
MC
Glen
John
J
Rahme
Jeannie
J
Stankovic
Zvijezdana
Z
Ramzan
Iqbal
I
Murray
Michael
M
McLachlan
Andrew J
AJ
D001711:Biotransformation; D002110:Caffeine / Q000493:pharmacokinetics; D002853:Chromatography, Liquid; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D003915:Dextromethorphan / Q000493:pharmacokinetics; D006801:Humans; D019808:Losartan / Q000493:pharmacokinetics; D008874:Midazolam / Q000493:pharmacokinetics; D009853:Omeprazole / Q000493:pharmacokinetics; D010641:Phenotype; D053719:Tandem Mass Spectrometry
D002110:Caffeine; D003915:Dextromethorphan; D003577:Cytochrome P-450 Enzyme System; D019808:Losartan; D009853:Omeprazole; D008874:Midazolam