Pharmacokinetic study on the interaction between succinic acid and irbesartan in rats and its potential mechanism

CONTEXT: Succinic acid and irbesartan are commonly used drugs in cardiovascular disease treatment. The interaction might occur during their co-administration, which was still unclear. OBJECTIVE: To reveal the effect of succinic acid on the metabolism of irbesartan and its potential mechanism. MATERIALS AND METHODS: The Sprague-Dawley rats (n = 6) were treated with a single dose of 30 mg/kg irbesartan (control) or the co-administration with the pre-treatment of 200 mg/kg succinic acid for 7 d. The effect of succinic acid on the metabolic stability and the activity of CYP2C9 was evaluated in rat liver microsomes. RESULTS: Succinic acid increased the AUC (5328.71 ± 959.31 μg/L × h vs. 3340.23 ± 737.75 μg/L × h) and prolonged the half-life of irbesartan (from 12.79 ± 0.73 h to 20.59 ± 6.35 h). The T(max) (2.83 ± 0.75 h vs. 3.83 ± 1.10 h) and clearance rate (3.46 ± 1.13 L/h/kg vs. 6.91 ± 1.65 L/h/kg) of irbesartan was reduced by succinic acid. Consistently, succinic acid improved the metabolic stability (half-life from 23.32 ± 3.46 to 27.35 ± 2.15 min, intrinsic clearance rate from 59.43 ± 6.12 to 50.68 ± 5.64 μL/min/mg protein). Succinic acid was also found to inhibit the activity of CYP2C9 with the IC(50) value of 13.87 μM. DISCUSSION AND CONCLUSIONS: Succinic acid increased the system exposure of irbesartan via inhibiting CYP2C9. The experiment design of this study also provides a reference for the further validation of this interaction in humans.