Possible Interaction: Quercetin and Tamoxifen

“In summary, the findings of the present study suggest that quercetin when associated with tamoxifen decreases in plasma glucose levels.”

“The BuChE activity decreased in the … at all tested doses of quercetin coadministered … tamoxifen (P < .01); however, in adipose tissue, there was a biphasic activity with a decrease (P < .05) and increase (P < .05) in activity at doses of 7.5 and 22.5 mg.kg-1 b.w.”

“These findings indicate that tamoxifen inhibits CWR22 prostate tumor by modulating the angiogenesis and its antineoplastic effects can be potentiated by combined use with quercetin.”

“This suggests that quercetin can reverse tamoxifen resistance in breast cancer cells.”

“Combinations of ERbeta ligands such as estradiol (E(2)), 17 epiestriol (17E(3)), quercetin (Q) with tamoxifen (TMX) showed marked growth inhibition.”

“Competition analysis showed that the anti‐estrogen tamoxifen and the flavonoids quercetin and rutin competed for (3H)‐E2 binding to type‐II EBS.”

“If the results are further confirmed in the clinical trials, the tamoxifen dosage should be adjusted when tamoxifen is administered with quercetin or quercetin-containing dietary supplements in order to avoid potential drug interactions.”

“The absolute bioavailability (AB%) of tamoxifen with 2.5 and 7.5 mg/kg quercetin ranged from 18.0% to 24.1%, which was significantly higher than the control group, 15.0% (p < 0.05).”

“The coadministration of quercetin (2.5 and 7.5 mg/kg) significantly (p < 0.05) increased the absorption rate constant (K(a)), peak concentration (C(max)) and the areas under the plasma concentration-time curve (AUC) of tamoxifen.”

“The enhanced bioavailability of tamoxifen as a result of its coadministration with quercetin might be due to the effect of quercetin promoting the intestinal absorption and reducing the first-pass metabolism of tamoxifen.”

“The relative bioavailability (RB%) of tamoxifen coadministered with quercetin was 1.20-1.61 times higher than the control group.”

“This suggests that quercetin inhibits the both MDR transporters efflux and first-pass metabolism of tamoxifen.”

“ Tamoxifen , in turn, significantly increased muscle relaxation at all quercetin concentrations.”