Studies were conducted to characterize the effect of dose and route of administration on the disposition of N-butylpyridinium chloride (NBuPy-Cl), an ionic liquid with solvent properties. Urine was the major route of NBuPy-Cl excretion after intravenous (5 mg/kg), single oral (0.5, 5, or 50 mg/kg), or repeated oral (50 mg/kg/day, 5 days) administration to male F-344 rats and single oral (50 mg/kg) administration to female B6C3F1 mice. Depending on the vehicle, absorption after dermal application (5 mg/kg, 125 microg/cm(2)) was 10 to 35% at 96 h. After the single intravenous dose, the blood concentration of NBuPy-Cl decreased in a biphasic manner with an elimination half-life of 2.2 h and a clearance of 7 ml/min. After single oral administration of NBuPy-Cl (50 mg/kg), maximum blood concentration was reached at 1.3 h, and the bioavailability was determined to be 47% at 6 h based on the blood toxicokinetics and 67% at 72 h based on urinary excretion. In all the urine and blood samples, only the parent compound was detected. Coadministration of NBuPy-Cl and inulin (by intravenous injection) revealed that the clearance of NBuPy-Cl exceeded the rat glomerular filtration rate. After incubation with Chinese hamster ovary cells expressing human organic cation transporter 2 (hOCT2), NBuPy-Cl was transported effectively (K(t) = 18 microM), and also a potent inhibitor of hOCT2 mediated tetraethylammonium transport (IC(50) = 2.3 microM). In summary, NBuPy-Cl is partially absorbed from the gastrointestinal tract and eliminated rapidly in the urine as parent compound most likely by renal glomerular filtration and OCT2-mediated secretion.