Topical dexamethasone decelerates epithelial migration on the canine tympanic membrane.

Background: Epithelial migration (EM) is integral to normal ear structure and function. Glucocorticoids are considered the first-line therapy for various external ear disorders; however, their effects on EM on the tympanic membrane (TM) and the external auditory canal (EAC) are understudied.

Hypothesis/objectives: To test the hypothesis that topical dexamethasone decelerates EM on the TM, this study aimed to evaluate the effects of topical dexamethasone on EM on the TMs of dogs.

Animals: Seven ears of four healthy dogs.

Materials and methods: The migration distance of an ink drop deposited on the posterior quadrant of the pars tensa (TM EM rate) of dogs was calculated over 3 weeks from images captured with a video-otoscope. The results were compared by paired Student's t-test to those obtained from a subsequent experiment in which the same dogs were administered a fresh ink drop at the same position as previously (control group), yet additionally administered 0.1% dexamethasone (0.2 mL/ear) daily for the first 14 days (treatment group).

Results: One of eight ears was excluded because of an anatomical problem. The TM EM rate of the remaining seven ears decreased by 46.74% in the treatment group compared with the control group (p < 0.05).

Conclusions and clinical relevance: Topical dexamethasone decelerates EM on the TM of normal dogs' ears. In turn, it is extrapolated that debris removal from the EAC may be slowed, negatively impacting the EAC environment. Consequently, when dogs with otitis receive topical dexamethasone treatment, additional treatment, such as ear canal cleaning, may be required to minimise the effects of impaired TM EM.