title: Steroids in aminoglycoside-containing ear drops: do they reduce cochlear toxicity?
abstract: OBJECTIVE
  To determine whether betamethasone (BM) reduces the cochlear toxicity of otic gentamicin (GM) if given together.
  
  
  METHODS
  Controlled animal study.
  
  
  METHODS
  Thirty-four mice were assigned at random to receive intratympanic injections of either 0.1 % BM (11 mice), 0.3% GM (13 mice), or a combination of both (GM/BM) with benzalkonium chloride (10 mice) in the left ear (treated) and saline on the right (untreated). Six injections were given on alternate days. Auditory brainstem response thresholds were assessed at 1 month, 2 months, and >2 months.
  
  
  RESULTS
  There was a significantly greater degree of hearing loss in the BM-treated ears compared to the untreated ears (6.48 dB hearing loss, P = .007) and in the GM-treated ears compared to untreated ears (6.59 dB hearing loss, P = .010,). However, otic GM/BM and benzalkonium chloride did not cause significant additional hearing loss compared with the untreated ears (3.56 dB hearing loss, P = .242).
  
  
  CONCLUSIONS
  Our data suggest that hearing loss caused by GM otic drops may be reduced by the inclusion of BM and benzalkonium chloride. Our finding that BM alone was associated with hearing loss suggests that the benzalkonium chloride may be the protective agent in combination otic drops.
authors.affiliation: Department of Otolaryngology, University of Manitoba, Winnipeg, Manitoba, Canada.
authors.forename: Brian W
authors.initials: BW
authors.lastname: Blakley
authors.forename: Saad
authors.initials: S
authors.lastname: Alsaleh
authors.forename: Zameel
authors.initials: Z
authors.lastname: Dewji
authors.forename: Kaiser
authors.initials: K
authors.lastname: Qureshy
authors.forename: Sylvie
authors.initials: S
authors.lastname: Berard
authors.forename: Ling
authors.initials: L
authors.lastname: Xie
mesh_terms: D000617:Aminoglycosides / Q000633:toxicity*; D000818:Animals; D001548:Benzalkonium Compounds / Q000494:pharmacology; D001623:Betamethasone / Q000494:pharmacology*; D003051:Cochlea / Q000187:drug effects*; D016057:Evoked Potentials, Auditory, Brain Stem; D007267:Injections; D051379:Mice; D008810:Mice, Inbred C57BL; D011897:Random Allocation
chemical_list: D000617:Aminoglycosides; D001548:Benzalkonium Compounds; D001623:Betamethasone
keywords: Hearing; aminoglycosides; antioxidants; auditory brainstem response; ototoxicity