Sound Exposure Promotes Intratympanic Drug Delivery to the Inner Ear

ObjectiveTo investigate the impact of sound exposure, with the resultant windows vibration on perilymphatic concentrations following intratympanic (IT) dexamethasone and gentamicin in an animal model.Study DesignAnimal model blinded study.SettingAnimal facility of a tertiary medical center.MethodsBilateral IT dexamethasone or gentamicin was applied to 15 tested rats. Following injections, each rat was exposed for 3 minutes to free field 30 dB sound pressure level (SPL), 512 vHz noise, with 1 external auditory canal plugged (contralateral control). Following noise exposure, perilymph was obtained from both ears. Drug concentrations were measured using ultrahigh-performance liquid chromatography-mass spectrometer.ResultsFor dexamethasone, the average (+/- SD) perilymphatic steroidal concentration was 0.417 mu g/mL (+/- 0.549) in the control ears versus 0.487 mu g/mL (+/- 0.636) in the sound-exposed ears (P = .008). The average (+/- SD) gentamicin perilymphatic concentration was 8.628 mu g/mL (+/- 2.549) in the sound-exposed ears, compared to 4.930 mu g/mL (+/- 0.668) in the contralateral control (nonsound exposed) ears. Sound exposure promoted steroidal and gentamicin diffusion to the inner ear by an averaged (+/- SD) factor of 1.431 and 1.730 (+/- 0.291 and 0.339), respectively.ConclusionLow-intensity noise (30 dB SPL) was found to enhance dexamethasone phosphate and gentamicin diffusion to the inner ear (by an averaged factor of similar to 1.4 and 1.7, respectively) in a murine model.