Background
Oxidative stress has been recently identified as the pivotal pathway of cochlear damage. The aims of this study were to evaluate whether distortion product otoacoustic emissions (DPOAEs) can discriminate normal subjects with a risk of damage induced by sound exposure, the effectiveness of OAEs in monitoring the protective effects of Coenzyme Q10 terclatrate (QTer), and the role of blood parameters in monitoring preventive therapies.
Material and Method
Twenty volunteers were randomized to two groups: the first (n=10) was treated with Q-Ter (200 mg orally once daily) for 7 days before noise exposure and the second group was treated with placebo using the same schedule. All participants were exposed to white noise of 90 dB HL for 15 minutes. DPOAEs and pure-tone audiometry (PTA) were measured before and 1 h, 16 h, and 7 and 21 days after exposure. Inflammatory and oxidative stress parameters were measured before and 2 and 24 h after exposure.
Results
In the placebo group, DPOAE amplitudes were reduced 1 and 16 h after exposure compared with the baseline values (p<0.05). In the Q-Ter group, DPOAEs did not show any significant difference between baseline and post-exposure (p>0.1). PTA threshold values in the Q-Ter and placebo groups did not differ before and after exposure. No significantly different levels of the inflammatory markers were observed in the Q-Ter and placebo groups at the different time points.
Conclusions
This pilot study confirms that DPOAEs represent a sensitive test for monitoring the effects of noise in preclinical conditions and pharmacological treatment.

Keywords: Protective Agents - pharmacology, Placebos, Pilot Projects, Oxidative Stress - drug effects, Otoacoustic Emissions, Spontaneous - physiology, Noise - adverse effects, Monitoring, Physiologic, Inflammation - blood, Biological Markers - blood, Audiometry, Pure-Tone, Antioxidants - pharmacology, Administration, Oral, Time Factors