Table 1.

Summary of definitions for “true” p-glycoprotein (P-gp) inhibitors, P-gp substrates or non-substrates.

Definition	P-gp Inhibition	ATPase activation	Efflux
“True” inhibitor	Y	N	N
Substrate	Y	Y	Y
Non-substrate	N	N	N

Inhibition assay, Y: inhibitor; ATPase activation, Y: activator; efflux, Y: effluxed compound.