Intestinal Absorption of HMG-CoA Reductase Inhibitor Pitavastatin Mediated by Organic Anion Transporting Polypeptide and P-Glycoprotein/Multidrug Resistance 1

Summary:The purpose of this study was to investigate the involvement of organic anion transporting polypeptide (OATP/Oatp) and P-glycoprotein (P-gp)/multidrug resistance 1 (MDR1/Mdr1) in intestinal absorption of pitavastatin. Pitavastatin was found to be a substrate for human OATP1A2, OATP2B1, and MDR1 and rat Oatp1a5, Oatp2b1, and Mdr1a in experiments using transporter-expressing Xenopus oocytes and LLC-PK1 cell systems. Naringin inhibited Oatp1a5- and Mdr1a-mediated transport of pitavastatin with IC 50 values of 18.5 and 541 μM, respectively. The difference in the IC 50 values of naringin for Oatp1a5 and Mdr1a-mediated pitavastatin transport may account for the complex concentrationdependent effect of naringin on the intestinal absorption of pitavastatin. Rat intestinal permeability of pitavastatin measured by the in situ closed-loop perfusion method was indeed significantly reduced by 200 μM naringin, but was significantly increased by 1000 μM naringin. Furthermore, the permeability was significantly increased by elacridar, a potent inhibitor of Mdr1, while the permeability was significantly decreased in the presence of both elacridar and naringin, suggesting that Oatp1a5 and Mdr1a are both involved in intestinal absorption of pitavastatin. Our present results indicate that OATP/Oatp and MDR1/ Mdr1 play roles in the intestinal absorption of pitavastatin as influx and efflux transporters, respectively.