Clinical trials supported by the Tinnitus Research Consortium: Lessons learned, the Southern Illinois University experience.

The Tinnitus Research Consortium funded three clinical trials investigating treatments for chronic bothersome tinnitus at Southern Illinois University School of Medicine. The trials were designed to measure the subjective changes in tinnitus distress using standardized questionnaires and objective changes in tinnitus loudness using psychophysical matching procedures. The results of the first two trials have been published and are summarized here. The first trial investigated the effect of gabapentin on the loudness and annoyance of tinnitus in adults with chronic bothersome tinnitus with and without a history of acoustic trauma. A small but significant number of subjects reported decreased tinnitus annoyance that corresponded with a decrease in objective measures of tinnitus loudness during active drug treatment with a washout effect during placebo treatment. The second trial compared the effect of tinnitus retraining therapy (TRT) on adults with normal to near-normal hearing and chronic bothersome tinnitus to treatment with general counseling without acoustic enrichment. Significant improvements in tinnitus severity, but not in objective psychometric measures of tinnitus loudness, occurred in both treatment groups, however a greater effect was observed in the TRT group compared with the control group. The third trial is nearing completion and investigates the long-term results of tinnitus retraining therapy on chronic bothersome tinnitus in adults with hearing loss. Significant lessons and observations on conducting tinnitus clinical trials were learned from these three trials. The challenges of recruiting and retaining study participants is discussed. More importantly, the reliability and stability of the Tinnitus Handicap Inventory (THI) over long intervals is presented. The implications of this variability for the design and interpretation of future tinnitus studies is discussed. This article is part of a Special Issue entitled <Tinnitus>.