<p>1. Plasma concentrations of curcumin-O-glucuronide (COG) and curcumin-O-sulfate (COS) significantly increased after Sprague-Dawley rats dealt with the Oatp inhibitor rifampicin, with the <i>C</i><sub>max</sub> ascending 2.9 and 6.7 times, and the AUC<sub>0–∞</sub> ascending 4.4 and 10.8 times, respectively. When pretreated with the Oat inhibitor probenecid, the <i>C</i><sub>max</sub> increased 4.4 and 20 times, and the AUC<sub>0–∞</sub> increased 3.2 and 13.9 times, respectively. The results suggested that COG and COS may be the substrates of Oatp and Oat.</p> <p>2. The accumulation of curcumin significantly increased in organic anion transporting polypeptide (OATP)- and organic anion transporter (OAT)-transfected human embryonic kidney (HEK) 293 systems, which suggested that curcumin was a substrate of OATP1B1, OATP1B3, OATP2B1, OAT1, and OAT3; and COG was a substrate of OATP1B1, OATP1B3, and OAT3.</p> <p>3. Inhibition study using rosuvastatin as the substrate in OATP1B1- and OATP1B3-transfected cells indicated that curcumin was an OATP1B1 and 1B3 inhibitor, with IC<sub>50</sub> at 5.19 ± 0.05 and 3.68 ± 0.05 μM, respectively; the data for COG were 1.04 ± 0.01 and 1.08 ± 0.02 μM, respectively. COS was speculated to be an inhibitor of hepatic OATP1B1 as calculated using the ADMET Predictor.</p> <p>4. COG and COS are substrates and inhibitors of OATP/Oatp. Co-administration of curcumin significantly increased rosuvastatin concentration in rat and dog plasma.</p