Effect of Rumex AcetosaExtract, a Herbal Drug, on the Absorption of Fexofenadine

Abstract

Herbal drugs are widely used for the auxiliary treatment of diseases. The pharmacokinetics of a drug may be altered when it is coadministered with herbal drugs that can affect drug absorption. The effects of herbal drugs on absorption must be evaluated. In this study, we investigated the effects ofRumex acetosa (R. acetosa)extract on fexofenadine absorption. Fexofenadine was selected as a model drug that is a substrate ofP-glycoprotein (P-gp) and organic anion transporting polypeptide 1A2 (OATP1A2). Emodine-the major component ofR. acetosaextract-showedP-gp inhibition in vitro and in vivo. Uptake of fexofenadine via OATP1A2 was inhibited byR. acetosaextract in OATP1A2 transfected cells. A pharmacokinetic study showed that the area under the plasma concentration-time curve (AUC) of fexofenadine was smaller in theR. acetosaextract coadministered group than in the control group.R. acetosaextract also decreased aqueous solubility of fexofenadine HCl. The results of this study suggest thatR. acetosaextract could inhibit the absorption of certain drugs via intervention in the aqueous solubility and the drug transporters. Therefore,R. acetosaextract may cause drug interactions when coadministered with substrates of drug transporters and poorly water-soluble drugs, although further clinical studies are needed.