Oxymetazoline ototoxicity in a chinchilla animal model.

OBJECTIVE: To investigate possible ototoxic effects of a one-time application of oxymetazoline drops in a chinchilla animal model with tympanostomy tubes. Study Design. A prospective, controlled animal study. SETTING: The Research Institute of the Montreal's Children Hospital, McGill University Health Centre. SUBJECTS AND METHODS: Ventilation tubes were inserted in both ears of 12 animals. One ear was randomly assigned to receive oxymetazoline drops (0.5 mL). The contralateral ear did not receive any drops, serving as a control ear. OUTCOME MEASURES: Distortion product otoacoustic emissions were measured bilaterally for a wide range of frequencies (between 1 and 16 kHz) before and 1 day after the application of oxymetazoline in the experimental ears. Two months later, the animals were sacrificed and all cochleae were dissected out and processed for scanning electron microscopy. RESULTS: In this established chinchilla animal model, the measured distortion product otoacoustic emission amplitudes and the morphological appearance on scanning electron microscopy were similar for both control and experimental ears. CONCLUSION: Oxymetazoline did not cause ototoxicity in a chinchilla animal model 2 months after a single application via a tympanostomy tube.

Ototoxicity of triethanolamine polypeptide (cerumenex) in the chinchilla.

UNLABELLED: The use of earwax softeners and cerumenolytics to unblock the external auditory canal is increasing. Although reports on their effectiveness are available, data about their effect on hearing are limited. OBJECTIVE: To assess the effect of ototopic triethanolamine polypeptide oleate condensate 10% (Cerumenex) on hearing. STUDY DESIGN: Prospective, randomized, controlled trial in a chinchilla animal model. METHODS: Tympanostomy tubes were inserted in five chinchillas, and hearing was assessed with distortion product otoacoustic emissions (DPOAE) between 1 and 9 kHz prior to application and at days 1, 4, 30, and 100 postototopic application of Cerumenex. One ear received Cerumenex; the other ear served as control. Postmortem scanning electron microscopy was performed to assess the cochlear hair cells. RESULTS: A reduction in the mean DPOAE signal was shown in the ears treated with Cerumenex from the first day after treatment and throughout the study. Almost all tested frequencies were affected. Swelling, crusting, and fluid were observed in four of the five experimental ears. One animal also developed facial paralysis in the experimental side. Electron microscopy showed damage of the outer and inner hair cells in the Cerumenex-treated ears. CONCLUSIONS: In the chinchilla, when a tympanic perforation is present, Cerumenex causes a reduction in DPOAE signal and damage to the cochlear hair cells. Caution should be observed when prescribing this agent if the status of the tympanic membrane is unknown. Furthermore, its use without medical prescription should be discouraged because of the risk of ototoxicity and severe inflammatory reaction.

Ototoxicity of topical moxifloxacin in a chinchilla animal model.

OBJECTIVE: Ciprofloxacin is currently the only proven nonototoxic topical antibiotic. However, its widespread use has resulted in the emergence of antimicrobial resistance. There are also concerns that there is currently no safe alternative to ciprofloxacin for patients with a nonintact eardrum. We thus wished to evaluate whether a moxifloxacin solution is ototoxic when used topically in chinchilla ears in the presence of a pressure-equalizing tube (PET). STUDY DESIGN: A prospective, randomized, controlled trial was conducted in an animal model. METHODS: Twenty chinchillas were included in this study. After bilateral insertion of PETs, four drops of a moxifloxacin solution were delivered twice daily for 7 days in the randomly assigned experimental ear. The control ear received an equal amount of a solution of Ringer's lactate. Distortion product otoacoustic emissions (DPOAE) were recorded at baseline (after PET insertion) and at days 1, 3, 7, 14, and 28 after treatment initiation. RESULTS: When baseline DPOAE measurements were compared with the final measurements at day 28, moxifloxacin caused a statistically significant (P < .05) hearing loss (HL) in the experimental ears for the frequencies between 3.7 and 15 kHz. There was no significant change in hearing in the control ears. CONCLUSION: This represents the first study on the ototoxicity of topical moxifloxacin. Our results demonstrate that moxifloxacin causes HL when used with a nonintact tympanic membrane in a chinchilla animal model.