title: Rapid identification of the hepatic cytochrome P450 2C19 activity using a novel and noninvasive [13C]pantoprazole breath test.
abstract: We tested the hypothesis that the stable isotope [(13)C]pantoprazole is O-demethylated by cytochrome P450 CYP2C19 and that the (13)CO(2) produced and exhaled in breath as a result can serve as a safe, rapid, and noninvasive phenotyping marker of CYP2C19 activity in vivo. Healthy volunteers who had been genotyped for the CYP2C19(*)2, CYP2C19(*)3, and CYP2C19(*)17 alleles were administered a single oral dose of [(13)C]pantoprazole sodium-sesquihydrate (100 mg) with 2.1 g of sodium bicarbonate. Exhaled (13)CO(2) and (12)CO(2) were measured by IR spectroscopy before (baseline) and 2.5 to 120 min after dosing. Ratios of (13)CO(2)/(12)CO(2) after [(13)C]pantoprazole relative to (13)CO(2)/(12)CO(2) at baseline were expressed as change over baseline (DOB). Maximal DOB, DOB(15) to DOB(120), and area under the DOB versus time curve (AUC(0-120) and AUC(0-infinity)) were significantly different among three genotype groups (CYP2C19(*)1/(*)1, n = 10; CYP2C19(*)1/(*)2 or CYP2C19(*)1/(*)3, n = 10; and CYP2C19(*)2/(*)2, n = 5) with predicted extensive metabolizers (EMs), intermediate metabolizers (IMs), and poor metabolizers (PMs) of CYP2C19, respectively (Kruskal-Wallis test, p < 0.01); linear regression analysis indicated a gene-dose effect relationship (r(2) ranged between 0.236 and 0.522; all p < 0.05). These breath test indices were significantly lower in PMs than IMs (p < 0.05) or EMs (p < 0.01) of CYP2C19. [(13)C]Pantoprazole plasma exposure showed significant inverse correlation with breath test indices in the respective subjects (Pearson r = -0.74; p = 0.038). These feasibility data suggest that the [(13)C]pantoprazole breath test is a reliable, rapid, and noninvasive probe of CYP2C19 and seems to be a useful tool to optimize drug therapy metabolized by CYP2C19.
authors.affiliation: Indiana University School of Medicine, Indianapolis, IN 46202, USA. zdesta@iupui.edu
authors.forename: Zeruesenay
authors.initials: Z
authors.lastname: Desta
authors.forename: Anil
authors.initials: A
authors.lastname: Modak
authors.forename: Phuong D
authors.initials: PD
authors.lastname: Nguyen
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Lemler
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Kurogi
authors.forename: Lang
authors.initials: L
authors.lastname: Li
authors.forename: David A
authors.initials: DA
authors.lastname: Flockhart
mesh_terms: D053799:2-Pyridinylmethylsulfinylbenzimidazoles / Q000097:blood / Q000493:pharmacokinetics; D000293:Adolescent; D000328:Adult; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism*; D001944:Breath Tests; D002245:Carbon Dioxide / Q000378:metabolism; D065731:Cytochrome P-450 CYP2C19; D004791:Enzyme Inhibitors / Q000097:blood / Q000493:pharmacokinetics; D005260:Female; D005838:Genotype; D006801:Humans; D008099:Liver / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D000077402:Pantoprazole; D011110:Polymorphism, Genetic / Q000235:genetics; D055815:Young Adult
chemical_list: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D004791:Enzyme Inhibitors; D002245:Carbon Dioxide; D000077402:Pantoprazole; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19