PGP and Hypertension: 2015; Zhang et al. 2015). Verapamil was developed as a calcium channel blocker to treat hypertension, and it has been reported as a inhibitor of P-gp and some CYP enzymes (Piao et al. 2008; Zhu et al. 2017; Chen et al. 2018), therefore, the absorption of some drugs with poor oral bioavailability could be enhanced (Huang et al. 2018). Oridonin is a substrate of CYP3A4 and its transportation involves P-gp.