Forsythiaside stability in pretreated rat plasma and its pharmacokinetics after i.v. administration

Forsythiaside is very unstable and can be affected by different conditions. Studying the stability of forsythiaside in vivo would greatly aid in accurately measuring it and evaluating its pharmacokinetics. No thorough study has been performed examining its stability during bio-sample pretreatment processing. This study is the first to completely investigate forsythiaside stability in plasma sample pretreatment processing. The time and temperature were the two key factors that determined forsythiaside stability in plasma pretreatment. Spiked plasma samples stored at 25 °C for 0.5 h or at 0 °C for 4 h were stable, and plasma samples vortexed with an internal standard (IS) and ethyl acetate were stable at 25 °C for 2 h or −20 °C for 4 h. An organic phase that was evaporated at 25 °C had high stability at temperatures greater than 37 °C. The storage time of spiked plasma and the vortex-mixed samples exerted a tremendous influence on the stability of forsythiaside. The storage, centrifugation and evaporation temperatures played indispensable roles in forsythiaside stability. During sample preparation, the reconstitution and injection times satisfied the requirements necessary for measuring forsythiaside in a pharmacokinetic study. Treating the plasma samples under the conditions investigated in this study will ensure that the data and parameters will be stable and controllable for a pharmacokinetic study and will be suitable for measuring forsythiaside in rat plasma. Moreover, this study will be a reference for both stability in other bio-matrices and pharmacokinetic studies in further research.