The Influence of Paracetamol on the Penetration of Sorafenib and Sorafenib N-Oxide Through the Blood–Brain Barrier in Rats

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, I(SR+PA)) and rats receiving oral vehicle and sorafenib 100 mg/kg (n = 42, II(SR)). 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 (K(p)) 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 I(SR+PA) K(p) to group II(SR) K(p) ratio. RESULTS: Pharmacokinetic analysis revealed increased brain exposure to sorafenib and sorafenib N-oxide after co-administration of paracetamol. The brain maximum concentration (C(max)) and the AUC of the parent drug in the I(SR+PA) group compared with the II(SR) 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 K(p) 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.