Influence of Verapamil on Pharmacokinetics of Triptolide in Rats.

The aim of this study was to investigate the role of P-glycoprotein (P-gp) in the intestinal absorption of triptolide. In this research, the bidirectional transport of triptolide across Caco-2 cells was studied in vitro. Moreover, the pharmacokinetic profiles of orally administered triptolide with and without pretreatment with verapamil were determined in rats. A markedly higher transport of triptolide across Caco-2 cells was observed in the basolateral-to-apical direction and was abrogated in the presence of the P-gp inhibitor, verapamil. The result indicated that P-gp might be involved in the absorption of triptolide. When the rats were pretreated with verapamil, the C max of triptolide increased from 423.01 ± 19.59 to 565.33 ± 20.27 ng/mL (33.6 %), and the AUC0-6 h increased by approximately 57 % when co-administered with verapamil. It was demonstrated that P-gp was involved in the transport of triptolide, which might exhibit a role in limiting its absorption and attenuating the toxicity of triptolide.