Background and objective: Sorafenib is an oral, multikinase inhibitor with established single-agent activity in several tumor types. Sorafenib was moderately transported by P-glycoprotein (P-gp) and more efficiently by breast cancer resistance protein. The constitutive androstane receptor (CAR) is a ligand-activated transcription factor involved in P-gp regulation in the brain microvasculature. Paracetamol is a CAR activator. The purpose of this study was to investigate the effect of paracetamol on the brain uptake of sorafenib and sorafenib N-oxide.
Methods: The rats were assigned to two groups-rats receiving oral paracetamol 100 mg/kg and sorafenib 100 mg/kg (n = 42, ISR+PA) and rats receiving oral vehicle and sorafenib 100 mg/kg (n = 42, IISR). The sorafenib and sorafenib N-oxide concentrations in blood plasma and brain tissue were determined by a high-performance liquid chromatography method with ultraviolet detection. Brain-to-plasma partition coefficient (Kp) was calculated as a ratio of the area under the curve from zero to 24 h (AUC) in the brain and plasma. A drug targeting index (DTI) was estimated as the group ISR+PA Kp to group IISR Kp ratio.
Results: Pharmacokinetic analysis revealed increased brain exposure to sorafenib and sorafenib N-oxide after co-administration of paracetamol. The brain maximum concentration (Cmax) and the AUC of the parent drug in the ISR+PA group compared with the IISR group were greater by 49.5 and 77.8%, respectively, and the same parameters for the metabolite were higher by 51.4 and 50.9%. However, the Kp values of sorafenib and sorafenib N-oxide did not differ significantly between the two animal groups and the DTI values were close to 1.
Conclusion: Paracetamol increases exposure to sorafenib and sorafenib N-oxide in the brain, likely due to increased exposure in plasma.