TY - JOUR T1 - Enhancement of Oral Bioavailability of Ginsenoside 20(s)-Rh2 through Improved Understanding of its Absorption and Efflux Mechanisms JF - Drug Metabolism and Disposition JO - Drug Metab Dispos DO - 10.1124/dmd.111.040006 SP - dmd.111.040006 AU - Zhen Yang AU - Song Gao AU - Jingrong Wang AU - Taijun Yin AU - Yang Teng AU - Baojian Wu AU - Ming You AU - Zhihong Jiang AU - Ming Hu Y1 - 2011/01/01 UR - http://dmd.aspetjournals.org/content/early/2011/07/14/dmd.111.040006.abstract N2 - The development of ginsenoside 20(s)-Rh2 (Rh2s) as a chemoprevention agent is limited by its low oral bioavailability. The goals of this study were to determine the mechanisms responsible for its poor oral absorption and to improve its bioavailability by overcoming the barrier to its absorption. Comprehensive studies were conducted using the following models: 1) monolayers of Caco-2, parental and MDR1 overexpressing MDCKII cells; 2) pharmacokinetics in wild-type (WT) FVB, MDR1a/b knockout (MDR1a/b -/-) FVB and A/J mice; and 3) intestinal perfusion in WT, MDR1a/b -/- FVB and A/J mice. Two P-gp inhibitors verapamil and cyclosporin A substantially decreased efflux ratio of Rh2s from 28.5 to 1.0 and 1.2, respectively in Caco-2 cells. The intracellular concentrations of Rh2s were also significantly increased (2.3 and 3.9 fold) in the presence of inhibitors. Similar results were obtained when transcellular transport of Rh2s were determined using MDR1-overexpressing MDCKII cells in the absence or presence of cyclosporin A. Compared to WT mice, the plasma Cmax and AUC0-∞ of Rh2s were substantially increased by 17 and 23 fold in MDR1a/b -/- FVB mice, respectively. In the A/J mice, the oral bioavailability of Rh2s (0.94% at 5 mg/kg and 0.52% at 20 mg/kg) was substantially increased by P-gp inhibitor to 33.18% and 27.14%, respectively. As expected, deletion or inhibition of P-gp significantly increased absorption and steady-state plasma concentration of Rh2s in mouse intestinal perfusion model. In conclusion, Rh2s is a good substrate of P-gp and inhibition of P-gp can significantly enhance its oral bioavailability. ER -