[In vitro and in vivo biodegradation of sustained-release vehicle poloxamer 407 in situ gel].

Objective: To observe the biodegradation of poloxamer 407 gel in acoustic capsule in vitro and in vivo, and to explore the applied perspective in the local drug delayed-release treatment for inner ear disorders.

Method: Weighing the remained amount of poloxamer 407 gel at 37 degrees C at fixation time interval. The right ears of 15 healthy guinea pigs as experimental group were perfused with 20% poloxamer 407 solution 100 microl in round window niche, the left ears as control group with normal saline. The histology of bullae at 7, 14, 28, 49 days after perfusion was examined by means of serial section after paraffin imbedding.

Result: The degraded amount were 20% and 25% in two groups respectively. The poloxamer 407 gel at 37 degrees C after 7 weeks was (78.89 +/- 13.10) microg and (75.32 +/- 8.94) microg respectively. The poloxamer gel in bullae was almost biodegraded and discharged 49 days after perfusion, only few gel remained in the middle ear cavity under light microscope. The morphology of the mucosa of middle ear cavity and round window membrane were not significantly damaged after poloxamer 407 perfusion.

Conclusion: Poloxamer 407 biodegraded slowly, but it could be biodegraded in vivo or discharged via eustachian tube, and caused no inflammation and immunologic rejection on the middle ear cavity. Thus, poloxamer 407 gel is suitable for the short-time sustained-release medical treatment in the inner ear diseases.