Mashali 2016.

Methods	A 3‐armed (betahistine, carbamazepine and placebo), double‐blinded, parallel‐group randomised controlled trial with 12 weeks duration of treatment and 12 weeks duration of follow‐up
Participants	Location: Ahvaz, Iran Setting: single‐centre study, Department of Otorhinolaryngology, Ahvaz Jundishapur University of Medical Sciences, from May 2015 to May 2016 mentioned in the abstract and from August 2015 to August 2016 mentioned in the materials and methods section Sample size: Number randomised: not reported Number completed: 24 or 25 in betahistine group and 24 or 25 in placebo group Participant baseline characteristics: Age: no significant difference Gender: no significant difference Tinnitus severity (points on Tinnitus Severity Index (SD)): 33 (8) in betahistine group versus 33 (8) in placebo group Inclusion criteria: patients aged over 21 to 65 years with non‐pulsatile tinnitus with a duration of at least 6 months Exclusion criteria: Pulsatile tinnitus Ménière’s disease Neuroma Otosclerosis Hearing aid use Pregnancy Mental illness requiring treatment Intolerance or allergic reaction to the study drugs Use of antiepileptic medication, oral contraceptives or other medication that may interfere with carbamazepine Severe heart disease
Interventions	Intervention group: betahistine tablets, 16 mg daily (8 mg 2 times a day), 12 weeks Comparator group: placebo tablets, dosage and frequency not reported, 12 weeks Use of additional interventions: none reported
Outcomes	Tinnitus Severity Index (range 0 to 56 points) at 12 weeks
Funding sources	No information provided
Declarations of interest	No information provided
Notes	In the text of the results section the authors report 25 participants in the betahistine group and 24 participants in the placebo group. In table 1 the authors report 24 participants in the betahistine group and 25 participants in the placebo group.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Participants were randomly placed in 3 groups in terms of sex, age and tinnitus severity. Methods of randomisation were not reported.
Allocation concealment (selection bias)	Unclear risk	Methods of allocation concealment were not reported
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	In the introduction it was mentioned that this was a double‐blind trial. However, the authors did not report who was blinded for what.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	In the introduction it was mentioned that this was a double‐blind trial. However, the authors did not report who was blinded for what.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	The number of included participants was not mentioned in the materials and methods section. It is unclear whether the number of participants evaluated was the same as the number of participants initially allocated to the treatment groups.
Selective reporting (reporting bias)	High risk	The abstract and the materials and methods section mentions that audiometric tests were conducted as a pre‐ and postintervention measure, but these were not reported in the results section
Other bias	Unclear risk	Conflicts of interest and funding were not reported

SD: standard deviation