Capsaicin induces metabolism of simvasatin in rat: involvement of upregulating expression of Ugt1a1.

Capsaicin (CAP, trans-8-methyl-N-vanillyl-6-nonenamide) is a major pungent substance in hot pepper. However, little is known about the interactions between CAP and clinically used drugs. This study investigated the effect of acute and chronic ingestion of CAP on pharmacokinetics of simvastatin (SV) and the mechanism of this CAP--drug intercation. CAP was orally administered at doses of 3 and 8 mg x kg(-1) for seven consecutive days once daily and on the 1st day and the 7th day, SV (8 mg x kg(-1)) was injected intravenously. Plasma concentrations of SV were determined using LC/MS/MS and expression of Ugt1a1 was analyzed by RT-qPCR and Western Blotting. We found that there were 78.0% (P < 0.05) and 81.2% (P < 0.05) reduction in the AUC(0-∞) of SV, respectively, following pretreatment with two doses of CAP. The AUC(0-∞) of SV in the two dose group pretreated with CAP for 7 days were decreased significantly, compared to the group for 1 day. Both the RT-qPCR and Western Blotting data indicated that 7 days pretreatment with CAP increased the expression level of Ugt1a1 in liver. In conclusion, chronic ingestion of CAP enhanced the expression level of Ugt1a1 in liver, causing the food -drug interaction and decrease in SV exposure in rats to a significant extent.