BACKGROUND/AIMS: The kinetics of omeprazole and its primary metabolites 5'-hydroxyomeprazole and omeprazole sulfone were studied in healthy volunteers to evaluate omeprazole as a probe drug for the S-mephenytoin hydroxylase (CYP2C19) polymorphism. The plasma metabolic ratio obtained from the concentrations of omeprazole plus omeprazole sulfone over 5'-hydroxyomeprazole was investigated. METHODS: The time course of the omeprazole metabolic ratio was studied in 14 extensive metabolizers, one intermediate, and five poor metabolizers of CYP2C19 after a 1-week administration of 40 mg/d omeprazole. The ratio was then determined in 187 randomly selected Caucasian hospital patients and analyzed according to liver disease and co-medication. RESULTS: Between 1 and 4 h after omeprazole intake, the volunteers phenotyped by the urinary S/R-mephenytoin ratio were reliably identified as extensive metabolizers and poor metabolizers by an omeprazole metabolic ratio-antimode of 12. This antimode remained valid in eight extensive metabolizers and one poor metabolizer, who were re-investigated with 60 mg omeprazole b.i.d. for one week. Among 30 patients without concomitant drug intake, only one poor metabolizer (3.3%) was identified by both the S/R-mephenytoin ratio and omeprazole metabolic ratio. However, 30 of 47 patients with liver disease and 20 of 110 co-medicated patients without liver disease had a ratio > 12. This highly exceeded the poor metabolizer frequency of 3-4% in Caucasians. CONCLUSIONS: Like other phenotypic tests, the omeprazole metabolic ratio appears to reflect CYP2C19 genotype reliably only in individuals without liver disease or co-medication. The omeprazole metabolic ratio may serve the double purpose of phenotyping for CYP2C19 and to individualize dosing in omeprazole-treated patients.
BACKGROUND/AIMS: The kinetics of omeprazole and its primary metabolites 5'-hydroxyomeprazole and omeprazole sulfone were studied in healthy volunteers to evaluate omeprazole as a probe drug for the S-mephenytoin hydroxylase (CYP2C19) polymorphism. The plasma metabolic ratio obtained from the concentrations of omeprazole plus omeprazole sulfone over 5'-hydroxyomeprazole was investigated. METHODS: The time course of the omeprazole metabolic ratio was studied in 14 extensive metabolizers, one intermediate, and five poor metabolizers of CYP2C19 after a 1-week administration of 40 mg/d omeprazole. The ratio was then determined in 187 randomly selected Caucasian hospital patients and analyzed according to liver disease and co-medication. RESULTS: Between 1 and 4 h after omeprazole intake, the volunteers phenotyped by the urinary S/R-mephenytoin ratio were reliably identified as extensive metabolizers and poor metabolizers by an omeprazole metabolic ratio-antimode of 12. This antimode remained valid in eight extensive metabolizers and one poor metabolizer, who were re-investigated with 60 mg omeprazole b.i.d. for one week. Among 30 patients without concomitant drug intake, only one poor metabolizer (3.3%) was identified by both the S/R-mephenytoin ratio and omeprazole metabolic ratio. However, 30 of 47 patients with liver disease and 20 of 110 co-medicated patients without liver disease had a ratio > 12. This highly exceeded the poor metabolizer frequency of 3-4% in Caucasians. CONCLUSIONS: Like other phenotypic tests, the omeprazole metabolic ratio appears to reflect CYP2C19 genotype reliably only in individuals without liver disease or co-medication. The omeprazole metabolic ratio may serve the double purpose of phenotyping for CYP2C19 and to individualize dosing in omeprazole-treated patients.
Authors: Y Khaliq; K Gallicano; I Seguin; K Fyke; G Carignan; D Bulman; A Badley; D W Cameron Journal: Br J Clin Pharmacol Date: 2000-08 Impact factor: 4.335
Authors: Rebekah L I Crake; Matthew R Strother; Elisabeth Phillips; Matthew P Doogue; Mei Zhang; Chris M A Frampton; Bridget A Robinson; Margaret J Currie Journal: Sci Rep Date: 2021-03-11 Impact factor: 4.379