Duphar 77054 1983.

Study characteristics
Methods	Allocation: randomised, but no further detail Design: prospective, parallel‐group, single centre
Participants	Number: 50 randomised Age: up to 70 Gender: 22 M, 14 F Setting: specialist centre Eligibility criteria: vertigo "likely to be of peripheral origin", "stable for 2 or 3 months"Exclusion criteria: other significant medical conditions (specified in report) Baseline characteristics: data provided in Table I and Table III of paper
Interventions	Betahistine 12 mg 3 times a day versus placebo for 12 weeks Intervention group: n = 19 Comparator group: n = 17 Use of additional interventions: none
Outcomes	Primary outcome: vertigo severity (4‐point ordinal scale)Secondary outcomes: adverse effects
Funding sources	Unpublished manufacturer data
Declarations of interest	Unpublished manufacturer data
Notes	Unpublished study
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	"Randomised", no further information
Allocation concealment (selection bias)	Unclear risk	Method not stated
Blinding of participants and personnel (performance bias) All outcomes	High risk	Envelopes provided to participants stating allocation; returned sealed envelope collection not reported; opacity not stated
Blinding of outcome assessment (detection bias) All outcomes	High risk	"Double blind", but no further information
Incomplete outcome data (attrition bias) All outcomes	High risk	50 randomised, 33 analysed; betahistine participants dropped out due to increased symptoms or high anxiety levels making assessment difficult; analysis is "as treated" Participants lost to follow‐up: 14
Selective reporting (reporting bias)	Unclear risk	No protocol available for inspection
Other bias	Unclear risk	No exclusion of participants who had previously taken betahistine