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Atypical cytochrome P450 3A4 (CYP3A4) enzyme activity-induced and inhibited-is thought to be the driver of numerous poor or adverse therapeutic responses to up to 50 % of all commonly prescribed drugs. We carried out a genome-wide association study to identify common genetic variants associated with variation in induced CYP3A4 activity. A total of 310 twins were included in this study. Each participant had already completed a 14 days course of St John's Wort to induce CYP3A4, which was quantified through the metabolic ratio of exogenous 3-hydroxyquinine to quinine. We failed to detect any genome-wide significant associations (P 

Original publication




Journal article


Eur J Drug Metab Pharmacokinet

Publication Date





63 - 67


Aged, Aged, 80 and over, Biomarkers, Biotransformation, Cytochrome P-450 CYP3A, Enzyme Induction, Female, Genome-Wide Association Study, Genotype, Humans, Hydroxylation, Hypericum, Liver, Middle Aged, Phenotype, Plant Preparations, Quinidine, Quinine, Substrate Specificity, Twins