Pharmacokinetic study on the interaction between pachymic acid and bavachin and its potential mechanism

ContextPachymic acid and bavachin are commonly used drugs in the therapy of lung cancer.ObjectiveThe co-administration of pachymic acid and bavachin was investigated to evaluate their potential drug-drug interaction.Materials and methodsThe pharmacokinetics of bavachin (10 mg/kg) was studied in male Sprague-Dawley (SD) rats in the presence of pachymic acid (5 mg/kg) (n = 6). The rats without pre-treatment of pachymic acid were set as the control and the pre-treatment of pachymic acid was conducted for 7 days before the administration of bavachin. The effect of pachymic acid on the activity of CYP2C9 was also estimated in rat liver microsomes with corresponding probe substrates.ResultsPachymic acid influenced the pharmacokinetic profile of bavachin with the increased AUC (32.82 ± 4.61 vs. 19.43 ± 3.26 μg/L/h), the prolonged t_1/2 (3.21 ± 0.65 vs. 2.32 ± 0.28 h), and the decreased CLz/F (307.25 ± 44.35 vs. 523.81 ± 88.67 L/h/kg) in vivo. The metabolic stability of bavachin was enhanced by pachymic acid and the transport of bavachin was inhibited by pachymic acid. Pachymic acid was found to inhibit the activity of CYP2C9 with the IC₅₀ of 21.25 µM as well as the activity of P-gp.Discussion and conclusionThe interaction between pachymic acid and bavachin results from the inhibition of CYP2C9 and P-gp. The dose of bavachin should be adjusted when combining with pachymic acid. The study design can be generalized to a broader study population with adjustment in the dose.