<p><b>OBJECTIVE</b>To 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.</p><p><b>
METHODS</b>The 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.</p><p><b>RESULTS</b>The
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.</p><p><b>CONCLUSIONS</b>
Poloxamer 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.</p>