Objective: To investigate the release properties of geranium tannins colon-specific preparation in vitro . Method: The pellets were prepared by using calcium pectinate as a carrier

Geranium tannins as the model drug to fill in the intestines dissolving capsule. The release of the preparation in different mediums in vitro was determined with gallic acid as the index. Result: The accumulated percentage of release rate of pellets in simulated gastrointestinal fluid was less than 10%

but in the simulated colonic fluid which contained 0.5% pectin enzyme

the accumulated percentage of release rate reached 80% within 4 hours. Conclusion: The preparation had the characteristics as a colon-specific delivery system.