Carbamazepine: a 'blind' assessment of CYP-associated metabolism and interactions in human liver-derived in vitro systems |
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Authors: | O. Pelkonen P. Myllynen P. Taavitsainen A. R. Boobis P. Watts B. G. Lake |
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Affiliation: | 1. University of Oulu, Department of Pharmacology and Toxicology, PO Box 5000, FIN-90014 Oulu, Finland;2. Imperial College School of Medicine, Department of Medicine, Section of Clinical Pharmacology, London, UK;3. TNO BIBRA International Ltd, Carshalton, UK |
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Abstract: | 1. The ability of various in vitro systems for CYP enzymes (computer modelling, human liver microsomes, precision-cut liver slices, hepatocytes in culture, recombinant enzymes) to predict various aspects of in vivo metabolism and kinetics of carbamazepine (CBZ) was investigated. 2. The study was part of the EUROCYP project that aimed to evaluate relevant human in vitro systems to study drug metabolism. 3. CBZ was given to the participating laboratories without disclosing its chemical nature. 4. The most important enzyme (CYP3A4) and metabolic route (10,11-epoxidation) were predicted by all the systems studied. 5. Minor enzymes and routes were predicted to a different extent by various systems. 6. Prediction of a clearance class, i.e. slow clearance, was correctly predicted by microsomes, slices, hepatocytes and recombinant enzymes (CYP3A4). 7. The 10,11-epoxidation of CBZ by the recombinant CYP3A4 was enhanced by the addition of exogenous cytochrome-b5, leading to a considerable over-prediction. 8. Induction potency of CBZ was predicted in cultured hepatocytes in which 7- ethoxycoumarin O-deethylase was used as an index activity. 9. It seems that for a principally CYP-metabolized substance such as CBZ, all liverderived systems provide useful information for prediction of metabolic routes, rates and interactions. |
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