Valsartan is a potent, orally active non-peptide tetrazole derivative and selectively inhibits angiotensin II receptor type 1 which causes reduction in blood pressure and is used in treatment of hypertension. The risk of heart disease mortality decreased significantly as flavonoid intake increased. Interestingly, the flavonoid-containing foods contain a high amount of Quercetin. The objective of this study was to evaluate the influence of quercetin on the pharmacokinetics of valsartan. In vivo studies were performed on rats. Rats were treated with quercetin (10 mg/kg) and valsartan (10 mg/kg), blood samples were collected at 1, 1.5, 2, 2.5, 3, 3.5, 4, 6 and 8 h. Plasma concentration of valsartan was estimated by Reverse Phase (RP-HPLC). Quercetin significantly increases the plasma concentration of valsartan and peak concentration (70.45 µg/mL) was achieved at 3.5 h. In vitro studies were performed on rat intestinal everted sacs. The transport of valsartan from serosal side to mucosal side decreased from 53.12 ± 1.27 to 40.15 ± 0.45 µg/mL in the presence of quercetin and from 53.12 ± 1.27 to 28.68 ± 0.31 µg/mL in the presence of verapamil (standard P-glycoprotein (P-gp) inhibitor) at 120 min. Verapamil is a potent P-gp and CYP3A4 inhibitor. Quercetin is a P-gp inhibitor and may be an inhibitor of CYP3A4. The simultaneous administration of quercetin significantly increases the intestinal absorption and decreases the efflux of valsartan. The observed effect may be beneficial to develop oral valsartan dosage forms using safe P-gp inhibitor (quercetin) to improve its oral bioavailability.

No abstract

The study was undertaken to evaluate the effect of quercetin on the pharmacokinetics of Metoprolol tartrate. A single dose in vivo pharmacokinetic study was carried out in rat models. In this study, rats were treated with quercetin (10 mg/kg) and metoprolol tartrate (20 mg/kg) orally and blood samples were collected 0, 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 8, 12 h post treatment. Plasma concentration of metoprolol tartrate was estimated using reverse phase-high-performance liquid chromatography method. Area under the plasma concentration-time curve (AUC0-12) of metoprolol has significantly (P < 0.001) decreased by 9.8 times in the metoprolol and quercetin combination group (9434.65 ± 3525.02) when compared with AUC0-12 metoprolol of metoprolol-alone treated group (962.17 ± 242.81). AUC0-∞ of metoprolol has significantly (P < 0.001) decreased by 14.9 times in the combination group (16670.79 ± 12129.06) in comparison to AUC0-∞ of metoprolol of metoprolol-alone treated group (1113.68 ± 441.83). the results obtained herein indicate that quercetin remarkably declines the plasma exposure of metoprolol when concomitantly administered by oral route.