Objective: To investigate in vivo release behaviour of 5-aminosalicylic acid(5-ASA) colon-specific pellets in rats

which based on osmotic pump enzyme trigger principle

and evaluate its colon localization release characteristics. Method: 5-ASA colon-specific pellets (the pellet group) with 5-ASA sodium carboxymethyl cellulose suspension(the control group) were given to rats by intragastric administration respectively

then got blood from rat heart in predetermined time intervals

and removed the stomach

small intestine

cecum

colon and their contents

relative targeted release index(DDI value) of them were calculated;Pellets' surface structure of different parts were observed by scanning electron microscope. Result: DDI value of the pellets group in the stomach

small intestine

cecum and colon were 11.09

12.08

187.25

181.68

respectively.We could observe that pellets had clearly visible aperture in the colon by scanning electron microscope. Conclusion: 5-ASA colon-specific pellets had good drug release in colon-specific.