Severe tinnitus induced by off-label baclofen

Abstract

Objective: The γ-aminobutyric acid type B (GABA-B) receptor agonist baclofen is approved for spasticity up to the dose of 80 mg/d. Recently, off-label use of high-dose baclofen (HDB), up to 400 mg/d, has been increasing for treating alcohol use disorders (AUDs), although the efficacy and safety profiles of HDB are relatively unknown. We report 2 cases of tinnitus in patients treated with HDB for AUD.

Case summaries: The first case concerns a 60-year-old man who reported tinnitus when he reached a 180 mg/d dose of baclofen after 3 months of treatment. Tinnitus persisted until the dose was reduced to 90 mg/d. The second case concerns a 45-year-old woman who presented with tinnitus when she reached a 210 mg/d dose of baclofen after 4 months of treatment. Tinnitus persisted until the dose was reduced to 60 mg/d.

Discussion: Using the Naranjo scale, imputability to baclofen was considered probable in both cases. GABA-B receptors have been reported to be implicated in both the etiology and the treatment of tinnitus. There may be an individual susceptibility to develop tinnitus under baclofen therapy because of some GABA-B genetic polymorphisms that remain to be determined.

Conclusion: HDB may be responsible for the occurrence of severe tinnitus, possibly in a dose-dependent manner. This appears to be coherent with the previously known involvement of GABA-B receptors in the pathophysiology of tinnitus.

Keywords: adverse drug reaction; alcohol dependence; baclofen; tinnitus.