Comparison with other studies
In the recent systematic review by Wegner et al.,3 the lack of rigorous clinical trials on Betahistine for primary tinnitus was evident, including only five studies. Also, it was not possible to prove the efficacy of this treatment (305 participants) as all studies had methodological flaws such as non-standardized outcome measures, heterogeneous dosages, unrepresentative samples, weak randomization, and unreliable blinding. Thus, the quality of evidence ranged from moderate to very low, making the results inconclusive.3
An alternative reference source of clinical trials using betahistine for tinnitus is studies pertaining to Ménière disease6. A recent systematic review failed to prove the efficacy of betahistine for Ménière symptoms such as tinnitus, also been represented by poor quality trials6. Although, unlike primary tinnitus studies, Adrion et al.18 conducted a multicentric high-quality trial testing low dose (2 x 24 mg daily) and high dose (3 x 48 mg daily) betahistine against placebo, giving more confidence to betahistine inefficacy. However, the extrapolation of these results for primary tinnitus is limited by possible differences in the pathophysiology of these conditions3.
In contrast to previous trials, Ganança et al.10conducted a case-control study of patients with tinnitus and vestibular symptoms showing beneficial effects of betahistine in cases as opposed to controls who received no treatment (32.5% vs. 17.1%). Its large sample was an advantage over the Wegner et al.3systematic review (865 vs. 305), but the poor control of bias of observational design compromised a valid conclusion of betahistine efficacy.