Drug interaction between Shoseiryuto Extract or Catechins and Fexofenadine through Organic‑Anion‑transporting Polypeptide 1A2 In vitro

Objective: Fexofenadine is an anti‑allergy drug frequently used to treat rhinitis, which is absorbed through organic‑anion‑transporting polypeptide (OATP) 1A2 in the intestine. Clinical studies have revealed that grapefruit juice inhibits OATP1A2 to reduce the absorption of fexofenadine. In Japanese traditional Kampo medicine, shoseiryuto, a formula composed of eight crude drugs, is frequently used to treat allergic rhinitis, especially cases of pollinosis. The objective of this study is to present the drug information regarding the interaction between shoseiryuto and fexofenadine through OATP1A2. Materials and Methods: We established human embryonic kidney 293 cells stably expressing OATP1A2 and evaluated the inhibitory effects of the extracts of shoseiryuto and its herbal components on the uptake of fexofenadine into the cells. Results: Shoseiryuto extract inhibited fexofenadine uptake in a concentration‑dependent manner with an IC50 value of 238 µg/ml. The inhibitory titer of shoseiryuto was much lower than that of grapefruit juice, and it is predicted that shoseiryuto could not pharmacokinetically interact interaction with fexofenadine through OATP1A2. Among the eight herbal components of shoseiryuto, the extracts of the terrestrial stem of Ephedra sinica and the root and stolon of Glycyrrhiza uralensis inhibited fexofenadine uptake with IC50 values of 102 and 89 µg/ml, respectively. We isolated catechin as the active ingredient from the extract of the terrestrial stem of E. sinica. Catechins inhibited the uptake of fexofenadine in a concentration‑dependent manner, and the IC50 values of epicatechin (EC) gallate, epigallocatechin (EGC) gallate, EGC, catechin, and EC were 11, 26, 41, 52, and 96 µM, respectively. Conclusion: These results would contribute to the safe and effective use of shoseiryuto in clinics.