Objective: To study the in situ intestinal absorption kinetics of bajijiasu in rats. Method: The absorption of bajijiasu in the small intestine (duodenum

jejunum and ileum) and colon of rats was investigated using an in situ single-pass perfusion method. The drug concentration was measured by HPLC-ELSD. The effects on intestinal absorption of different drug concentration (43.92

87.84

175.68 mg · L-1)

different pH in perfusate (5.4

6.8

7.4) and P-glycoprotein (P-gp)inhibitor (0

0.2

0.5 mmol · L-1) were conducted. Result: Bajijiasu could be absorbed in the whole intestine

and its absorption rate was influenced by the pH of the perfusion solution and intestinal segments. The absorption rate in duodenum

jejunum

ileum and colon was 2.752-2.861

1.435-1.574

1.353-1.403

1.144-1.301 h-1

respecvticvely

the rate declined in turn. Papp in the group containing the P-gp inhibitor increased markedly. Conclusion: The absorption of bajijiasu shows passive diffusion in the general intestinal segments with the first-order kinetic process.