In this study, tolterodine hydrogels which could form film after administration were prepared.We focused on the effect of ethyl acetate on the physicochemical characteristics of tolterodine hydrogels, including transparency, ability and time of film forming.Method to prepare the hydrogels was as follows, tolterodine tartrate was neutralized in the presence of absolute ethyl alcohol using excess KOH solution and precipitated phase was wiped out by centrifugation before the tolterodine hydrogels were prepared.Carbomer 980, hydroxypropyl cellulose (HPC) and hydroxypropyl methyl cellulose (HPMC) were swelled 12 h in beakers holding 6 ml deionized water.Then, the preprocessed alcohol solution of tolterodine free base was added to the matrices drop by drop with a sufficient mixing.Finally, different content of ethyl acetate (0%, 1%, 2%, 5%, 7%, 10% w/w) were added to the hydrogels.The result was showed in Figure 1.Addition of different content of ethyl acetate had different effects on the transparency of the hydrogels.With amount of ethyl acetate added increasing, the hydrogels gradually changed to a transparent state from a white opaque state.The mainly reason was that ethyl acetate played a role as a solubilizer for tolterodine free base in the hydrogels.Figure 2 showed the effect of ethyl acetate on film forming time.Film forming time was shorter than 5 min when amount of ethyl acetate added was below 5%, and the mechanical strength of film was strong and the film could be easily tom.As amount of ethyl acetate added increasing, film forming time would become longer.When the amount of ethyl acetate was raised to 10%, film forming time was longer than 20 min which might be too long for clinical application.As a conclusion that ethyl acetate was a good additive to improve the transparency of film-forming tolterodine hydrogels, besides, there was an optimum content which was 2%-5%.