Polyspecific organic cation transporters are critical for elimination of many endogenous small organic cations as well as a wide array of drugs and environmental toxins. SLC22A4 is an organic cation transporter and integral plasma membrane protein containing eleven putative transmembrane domains as well as a nucleotide-binding site motif. Transport by SLC22A4 is at least partially ATP-dependent. SLC22A4 may play a role in Crohn's disease.