Pharmacokinetic study of Gastrodia elata in rats

The pharmacokinetics of parishin, gastrodin, Gastrodia elata extract and Rhizoma Gastrodiae capsule was investigated by intragastric and/or intravenous administration to rats. Parishin was metabolized into nine metabolites after intravenous administration, and the area under the curve (AUC0–∞) of parishin and its metabolites (except parishin G and parishin E) increased nonlinearly from 72.5 to 220 mg/kg. When combining regression equation with the AUC0–∞ and dose of gastrodin injection, the percent conversion of parishin to gastrodin was obtained as 50 %. Based on multi-active metabolites of parishin in vivo, integrated pharmacokinetic mode was established. It is notable that each metabolite from parishin shares the similar metabolic process at three dosages of parishin and the bioavailability of parishin was approximately 14 %. The integrated pharmacokinetic mode was successfully applied to evaluate the holistic pharmacokinetics of gastrodin injection, G. elata extract and Rhizoma Gastrodiae capsule. The results showed that the holistic pharmacokinetics of gastrodin injection and G. elata extract was closed to that of gastrodin, but for parishin and Rhizoma Gastrodiae capsule, integrated pharmacokinetic parameters were more suitable to evaluate its holistic pharmacokinetics.