Blood samples (1–1.2 mL) were collected from each rat through the epicanthal vein at 15 min, 35 min, 1 h, 1.5 h, 2 h, 3 h, 4 h, 6 h, 8 h, 12 h, and 24 h after drug administration to investigate the effect of DXM on the pharmacokinetics of ATV and its metabolites. Then, plasma was separated from the blood by centrifugation (3500 rpm for 10 minutes at 4 ℃) and EDTA-K2 was used as the anticoagulant agent. On the 5th day of gavage administration, the animals were anesthetized with 7% chloral hydrate after oral dosing for 1 h. Based on the literature[13], a venous blood collection needle and a 1mL syringe with the needle removed were assembled, which was used to collect cerebrospinal fluid (CSF) of about 100 μL from the cisterna magna. If CSF is mixed with blood, it can be centrifuged at 4 ℃, 10000 rpm for 2 minutes, and then take the supernatant. In addition, the CSF and plasma samples were stored at -80 ℃ and -20 ℃, respectively, which were used to measure the drug concentration by LC-MS/MS later. After taking CSF and blood, the rat was perfused with ice PBS until the liver color changes from red to earthy yellow, and then the liver was excised, weighed, and stored at −80 ℃ until analysis.