OBJECTIVETo observe the biodegradation and absorption of poloxamer 407 in vivo, and the effect of poloxamer 407 on the middle ear and inner ear after regional perfusion in guinea pigs.

METHODSThe right ears of 10 guinea pigs as experimental group were perfused with 20% poloxamer 407 in situ gel 100 microl in round window niche, with the left ears as control group with normal saline. Another two animals without treatment were in negative control group. Auditory function was investigated before and 3, 7, 14, 28, 49 days after perfusion, and the histology of bulles after auditory brainstem response (ABR) each examination were examined by means of serial section after paraffin imbedding.

RESULTSThe poloxamer gel was almost biodegraded and discharged 49 days after perfusion, only few gel remained in the middle ear cavity under light microscope. The ABR threshold to filtered clicks was elevated after perfusion with poloxamer 407, and was recovered to normal at 49 days after perfusion. The morphology of the mucosa of middle ear cavity, round window membrane, Corti's and vestibular organs were not significantly damaged after poloxamer 407 perfusion.

CONCLUSIONSPoloxamer 407 can be biodagraded in vivo or discharged via eustachian tube, and causes no inflammation on the middle ear cavity. There are temporary changes on auditory function of inner ear after topical perfusion with poloxamer 407 in round window can cause, but no irreversible damage on function and morphology of cochlear and vestibular organs.