RESUMEN
This study aims to establish a rapid and sensitive UPLC-MS/MS method for simultaneously determining the content of strychnine and paeoniflorin in plasma and brain tissue of rats, and compare the pharmacokinetic behavior and brain tissue distribution of paeoniflorin combined with normal and toxic doses of strychnine in rats after percutaneous administration. Compared with those in the toxic-dose strychnine group, the AUC_(0-t), AUC_(0-∞), and C_(max) of strychnine decreased by 51.51%, 45.68%, and 46.03%, respectively(P<0.01), and the corresponding values of paeoniflorin increased by 91.41%, 102.31%, and 169.32%, respectively(P<0.01), in the compatibility group. Compared with the normal-dose strychnine group, the compatibility group showed insignificantly decreased C_(max), AUC_(0-t), and AUC_(0-∞) of strychnine, increased C_(max) and T_(max) of paeoniflorin(P<0.01), 66.88% increase in AUC_(0-t), and 70.55% increase in AUC_(0-∞) of paeoniflorin. In addition, the brain tissue concentration of strychnine decreased and that of paeoniflorin increased after compatibility. The combination of paeoniflorin with normal dose and toxic dose of strychnine can inhibit the percutaneous absorption of strychnine, and greatly promote the percutaneous penetration of paeoniflorin, whereas the interaction mechanism remains to be explored. The UPLC-MS/MS method established in this study is easy to operate and has good precision. It is suitable for in vivo study of pharmacokinetic behavior and brain tissue distribution of paeoniflorin and strychnine after percutaneous administration in rats, which provides reference for the safe and rational clinical use of strychnine and the combined use of drugs, and lays a solid foundation for the development of external preparations containing Strychni Semen.