LAUSR

Abstract Context Pachymic acid and bavachin are commonly used drugs in the therapy of lung cancer. Objective The co-administration of pachymic acid and bavachin was investigated to evaluate their potential drug-drug interaction. Materials and methods The 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. Results Pachymic 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 t1/2 (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 conclusion The 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.