P-glycoprotein substrates are compounds, including medications, that can be transported out of cells by p-glycoprotein. In the presence of intestinal p-glycoprotein inhibitors or inducers, the bioavailability of p-glycoprotein substrates may be increased or decreased, respectively.

For example, when p-glycoprotein activity in the intestines is inhibited, there are fewer available pumps removing the substrate from the intestinal cell, which can lead to more substrate being absorbed into the bloodstream (increased bioavailability). Alternatively, when p-glycoprotein activity is induced, there are more available pumps removing the substrate from the cell, which can result in less substrate being absorbed (decreased bioavailability).

The table below outlines some of the most common or clinically relevant p-glycoprotein substrates.​​ Importantly, this list is not exhaustive.^[1][2]