2.8.2. Pharmacokinetic Study

The pharmacokinetic study was performed on a rat model. The dose of *R. acetosa* extract evaluated was 2 g/kg, the maximum dose without the toxicity in rats (unpublished data). The selected oral dose of emodin was 11 mg/kg that inhibited *P*-gp mediated e fflux in rats from the reported study [32]. All test compounds—including 11 mg/kg of emodin and 2 g/kg of *R. acetosa* extract suspended in 0.5% carboxy methyl cellulose (CMC)—were administered orally to rats. Same volume of 0.5% CMC was administered to the vehicle control group rats. After 30 min, a single dose of 10 mg/kg of fexofenadine in 10% ethanol was orally administered to each group of rats [33]. Blood samples of 120 μL were collected from the carotid artery at each time point (0, 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 6, 8, 12 and 24 h) after oral administration of fexofenadine. The samples were then immediately centrifuged at 10,000× *g* and 4 ◦C for 10 min. All plasma samples were stored at −20 ◦C. The plasma concentrations of fexofenadine were determined by LC-MS/MS. All experimental procedures of the animal study were approved (GNU-170705-R0030, 5 July 2017) by the Animal Care and Use Committee of Gyeongsang National University, Korea.
