The primary objective of this clinical trial was to evaluate the efficacy of EGb 761® compared to placebo in preventing temporary noise-induced (bilateral 5 minutes 110 dB broadband noise) hearing impairment in 202 randomized (EGb 761® 100, placebo 102) healthy subjects.
Primary efficacy endpoint was the average increase of the audiometric threshold. Secondary endpoints has been decrease of TEOAEs, decrease of the contralateral suppression of TEOAEs, decrease of DPOAEs (growth function).
In the full analysis set (FAS), the primary efficacy endpoint, the mean average increase in audiometric thresholds was 9.9 dB in the EGb 761® group and 10.3 dB in the placebo group. The two-sided t-test was not able to detect a significant treatment effect (p = 0.5923). The secondary efficacy variable, “decrease of DPOAEs” measured by DPOAE growth function at 4004 Hz at V3 (SNR at all pairs of sound levels), was similar for both treatment groups before irradiation, whereas after irradiation, DPOAE SNR was consistently lower in the placebo group compared to the EGb 761® group at all five predefined sound levels. (ANCOVA p = 0.0104).
In summary, this trial could not establish efficacy of EGb 761® compared to placebo in preventing temporary noise-induced audiometric threshold shift in healthy subjects. With the tested subtoxic noise exposure and the chosen experimental setting, a protective effect of EGb 761® against noise induced hearing loss could not be demonstrated. A consistent effect (exploratory p = 0.01) in the most sensitive objective measure, the secondary endpoint DPOAE growth function at 4 kHz, might indicate a protective potential of EGb 761® that might become relevant at higher, toxic noise levels leading to permanent damage.
