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Abstract
The role of multidrug resistance-associated protein 2 (MRP2) on the intestinal disposition and hepatobiliary elimination of tenofovir disoproxil fumarate (DF) and its metabolites [tenofovir (mono)ester and tenofovir] was studied in the Caco-2 system, Ussing chambers and rat in-situ efflux experiments. In the Caco-2 model and Ussing chambers, no statistically significant differences in transport could be observed when the MRP inhibitor probenecid was included. In Ussing chambers, transport was also similar when using intestinal tissue from MRP2-deficient rats. After intravenous administration of tenofovir DF, the excretion of tenofovir [(mono)ester] in bile was significantly decreased in MRP2-deficient rats and in rats treated with probenecid. The area under the blood concentration–time curve was increased in MRP2-deficient rats [1.0 ± 0.1 and 0.36 ± 0.03 µM.min−1 for tenofovir and tenofovir (mono)ester, respectively] and rats treated with probenecid (1.42 ± 0.04 and 0.36 ± 0.02 µM.min−1) compared with control rats (0.64 ± 0.05 and 0.15 ± 0.06 µM.min−1). The appearance of tenofovir [(mono)ester] in intestinal perfusate was similar in control rats upon co-administering probenecid or when using MRP2-deficient rats. In conclusion, MRP2 appeared to have no modulatory effect on the intestinal disposition of tenofovir and tenofovir (mono)ester. However, inhibition (probenecid) or the total absence of MRP2 (MRP2-deficient rats) significantly reduced hepatobiliary elimination, which was accompanied by increased systemic exposure.
Acknowledgements
The study was supported by grants from the Flemish Fonds voor Wetenschappelijk Onderzoek (FWO) and from the Onderzoeksfonds of the K.U.Leuven, Belgium.