Otologic safety of intratympanic N-acetylcysteine in an animal model.

Objective: N-acetylcysteine (NAC) is an anti-oxidant and mucolytic effective against bacterial biofilms, making it useful in the treatment of chronically discharging ears that are unresponsive to traditional treatment methods. The objective of this study was to evaluate the otologic safety of intratympanic NAC combined with Ciprodex® in an animal model.

Methods: Baseline distortion product otoacoustic emissions (DPOAE) and auditory brainstem response (ABR) measurements were performed for both ears on thirteen guinea pigs from the animal care research facilities of the McGill University Health Center. This was followed by intratympanic administration of control solution (Ciprofloxacin 0.3%/Dexamethasone 0.1%) to the left ear and experimental solution (1.25% NAC/Ciprofloxacin 0.3%/Dexamethasone 0.1%) to the right ear. Three additional intratympanic injections were performed over the next fourteen days. DPOAE and ABR measurements were repeated 3-4 weeks after the initial procedure. Outcome measures included differences in DPOAE and ABR thresholds after intervention, clinical evidence of vestibular dysfunction and histological evidence of ototoxicity.

Results: There were no significant differences in the ABR thresholds and DPOAE results of the control and experimental ears at baseline and after intervention. There was neither clinical manifestation of vestibular dysfunction nor histological evidence of ototoxicity.

Conclusion: Our study suggests that intratympanic 1.25% NAC with ciprofloxacin and dexamethasone is safe in guinea pigs and support its potential use in the treatment of chronically discharging ears. Further studies in humans are required to analyze its efficacy relative to conventional treatments.

Level Of Evidence: Animal Research.