Intestinal P-glycoprotein: pharmacokinetic implications and approaches for enhancement of oral bioavailability of its substrates

A variety of drug transporters expressed in the body control the fate of drugs by affecting absorption, distribution, and elimination processes. In intestine, the transporters mediate the influx and efflux of endogenous or exogenous substances depending on their affinity to intestinal carrier systems as well as their chemical nature. Of prime interest are drug efflux pumps like P-glycoprotein that are recognized to pose functional role in determining the pharmacokinetics of drugs administered by peroral as well as parenteral route. Various formulation approaches are opted in order to overcome this P-glycoprotein mediated drug efflux. Moreover, broad substrate recognition by this protein and clinical implications of its inhibition lead to design and development of novel P-glycoprotein inhibitors that includes some therapeutic drugs and daily foods and beverages. Inhibition of P-glycoprotein improves intestinal absorption and tissue distribution while reducing the substrate metabolism and its elimination. Some of the pharmaceutical excipients have also shown P-glycoprotein inhibition activity. In this review, we will be discussing about the various approaches that can be explored to reduce P-glycoprotein mediated drug efflux and improve the bioavailability of its substrates.