A Cochrane review [Abstract] 1 included 7 studies with a total of 453 patients with tinnitus. The anticonvulsants gabapentin, carbamazepine, lamotrigine and flunarizine were studied. Three gabapentin studies (n=223) included a validated questionnaire for a primary outcome; none of them showed a significant positive effect. One study (n=30) showed a significant negative effect of gabapentin compared to placebo with an increase in Tinnitus Questionnaire (TQ) score of 18.4 points (SMD 0.82, 95% CI 0.07 to 1.58). Another study (n=114) showed a positive, non-significant effect of gabapentin with a difference to placebo of 2.4 points on the Tinnitus Handicap Inventory (THI) (SMD -0.11, 95% CI -0.48 to 0.25). When the data from these two studies were pooled, no effect of gabapentin was found (SMD 0.07, 95% CI -0.26 to 0.40). A third study (n=79) reported no differences on the THI after treatment with gabapentin compared to placebo (exact numbers not shown). A meta-analysis of 'any positive effect' (yes vs. no) based on a self-assessment score showed a small favourable effect of anticonvulsants (risk difference (RD) 14%, 95% CI 6% to 22%; 6 studies, n=420). A meta-analysis of 'near or total eradication of tinnitus annoyance' showed no effect of anticonvulsants (RD 4%, 95% CI -2% to 11%). Side effects of the anticonvulsants used were experienced by 18% of patients.
Comment: The quality of the evidence is downgraded by study quality (inadequate allocation concealment, lack of blinding, more than 20% loss to follow-up in some trials), inconsistency (heterogeneity in patients, treatments and outcomes) and imprecise results (limited study size for each comparison).
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