Transporter mechanisms on the cell membranes of hepatocytes. Proteins that are labeled yellow have known clinically relevant polymorphisms, while green labeled proteins do not have known clinically relevant polymorphisms. Abbreviations are used as follows: organic cation transporter (OCT), organic anion transporter (OAT), organic anion transporting polypeptide (OATP), Na+-taurocholate cotransporting polypeptide (NTCP), breast cancer resistance protein (BCRP), bile salt export pump (BSEP), multidrug resistance protein (MDR), multidrug resistance-associated protein (MRP), organic solute transporter (OST), and multidrug and toxin extrusion protein (MATE) [13].