Induction of Cytochrome P450 3A4 and P-Glycoprotein by the Isoxazolyl-Penicillin Antibiotic Flucloxacillin

Huwyler, Jörg and Wright, Matthew B. and Gutmann, Heike and Drewe, Juergen. (2006) Induction of Cytochrome P450 3A4 and P-Glycoprotein by the Isoxazolyl-Penicillin Antibiotic Flucloxacillin. Current Drug Metabolism, 7 (2). pp. 119-126.

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Clinical findings indicate that co-administration of the isoxazolyl-penicillin flucloxacillin with cyclosporine may reduce the plasma concentrations of cyclosporine. We have explored in the present study if induction of cytochrome P450 3A4 or P-glycoprotein may offer a mechanistic explanation of the observed effects. Flucloxacillin is neither an inhibitor nor a substrate of drug metabolizing cytochrome P450 isoenzymes (CYP3A4, 1A2, 2C9, 2C19 and 2D6) or P-glycoprotein as shown by an in vitro assay for CYP inhibition, a fluorescent indicator assay for P-glycoprotein inhibition and a functional P-glycoprotein ATPase assay. However, incubation of human LS 180 colorectal adenocarcinoma cells with flucloxacillin led to a dose-dependent induction of MDR1 as well as of CYP3A4 mRNA, which was also confirmed in primary human hepatocytes. At high concentrations, flucloxacillin activated the human Pregnane-X-Receptor, PXR, a ligand-dependent transcription factor that is the target of many drugs that induce CYP3A4, with consequences for the metabolism of other drugs. Liver microsomes from control rats or rats, which received for 3 consecutive days 100 mg/kg of oral flucloxacillin, were used to study the metabolism and metabolite pattern of midazolam, a model substrate of CYP 3A4. There was a trend towards a higher intrinsic microsomal clearance of midazolam using microsomes from flucloxacillin treated rats. In addition, there was a significant increase in the formation of the principal midazolam metabolites 1-hydroxy midazolam, 4-hydroxy midazolam and 1,4-dihydroxy midazolam as compared to controls. These findings indicate that flucloxacillin has the potential to induce expression of both CYP3A4 as well as P-glycoprotein, most likely through activation of the nuclear hormone receptor PXR. This would offer an explanation for the observed clinical drug-drug interactions between the antibiotic and cyclosporine.
Faculties and Departments:05 Faculty of Science > Departement Pharmazeutische Wissenschaften > Pharmazie > Pharmaceutical Technology (Huwyler)
UniBasel Contributors:Huwyler, Jörg
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Bentham Science Publishers
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:27 Nov 2017 11:11
Deposited On:27 Nov 2017 11:11

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