Utility of the auditory brainstem response evaluation in non-clinical drug safety evaluations

The Food and Drug Administration (FDA) requires thorough evaluation of the potential safety hazards of all new drugs, food additives, and therapeutic devices that are intended for human use. Drugs that are otically administered (i.e., ear drops), or are known to systemically distribute to the inner ear, require additional specialized safety testing to ensure that the drug does not permanently impair auditory function. To properly determine a drug's impact on auditory function, the FDA's Center for Drug Evaluation and Research requires the use of the Auditory Brainstem Response (ABR) evaluation. The ABR evaluation uses auditory stimuli evoked potentials to assess function by establishing minimum intensity thresholds. These thresholds can be monitored following drug treatment to determine an impact on hearing loss. This review discusses methodical considerations for conducting ABR evaluations as they apply to specialized drug safety studies. Alternative assays are discussed and compared to the utility of the ABR evaluation. Conclusions: The ABR evaluation provides reliable and sensitive measures of hearing function that are suitable for definitive drug safety evaluations or hazardous risk assessments.