Effects of curcumin on the pharmacokinetics of tamoxifen and its active metabolite, 4-hydroxytamoxifen, in rats: possible role of CYP3A4 and P-glycoprotein inhibition by curcumin
The effects of curcumin, a natural anti-cancer compound, on the bioavailability and pharmacokinetics of tamoxifen and its metabolite, 4-hydroxytamoxifen, were investigated in rats. Tamoxifen and curcumin interact with cytochrom P450 (CYP) enzymes and P-glycoprotein, and the increase in the use of health supplements may result in curcumin being taken concomitantly with tamoxifen as a combination therapy to treat or prevent cancer. A single dose of tamoxifen was administered orally (9 mg · kg−1) with or without curcumin (0.5, 2.5 and 10 mg · kg−1) and intravenously (2 mg · kg−1) with or without curcumin (2.5 and 10 mg · kg−1) to rats. The effects of curcumin on P-glycoprotein (P-gp) and CYP3A4 activity were also evaluated. Curcumin inhibited CYP3A4 activity with 50% inhibition concentration (IC50) values of 2.7 μM. In addition, curcumin significantly (P<0.01 at 10 μM) enhanced the cellular accumulation of rhodamine-123 in MCF-7/ADR cells overexpressing P-gp in a concentration-dependent manner. This result suggested that curcumin significantly inhibited P-gp activity. Compared to the oral control group (given tamoxifen alone), the area under the plasma concentration-time curve (AUC0–∞) and the peak plasma concentration (Cmax) of tamoxifen were significantly (P<0.05 for 2.5 mg · kg−1; P<0.01 for 10 mg · kg−1) increased by 33.1–64.0% and 38.9–70.6%, respectively, by curcumin. Consequently, the absolute bioavailability of tamoxifen in the presence of curcumin (2.5 and 10 mg · kg−1) was 27.2–33.5%, which was significantly enhanced (P<0.05 for 2.5 mg · kg−1; P<0.01 for 10 mg · kg−1) compared to that in the oral control group (20.4%). Moreover, the relative bioavailability of tamoxifen was 1.12- to 1.64-fold greater than that in the control group. Furthermore, concurrent use of curcumin significantly decreased (P<0.05 for 10 mg · kg−1) the metabolite-parent AUC ratio (MR), implying that curcumin may inhibit the CYP-mediated metabolism of tamoxifen to its active metabolite, 4-hydroxytamoxifen. The enhanced bioavailability of tamoxifen by curcumin may be mainly due to inhibition of the CYP3A4-mediated metabolism of tamoxifen in the small intestine and/or in the liver and to inhibition of the P-gp efflux transporter in the small intestine rather than to reduction of renal elimination of tamoxifen, suggesting that curcumin may reduce the first-pass metabolism of tamoxifen in the small intestine and/or in the liver by inhibition of P-gp or CYP3A4 subfamily.
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Document Type: Research Article
Publication date: 01 February 2012
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