Duphar H10800580M 1984.

Study characteristics
Methods	Allocation: randomised, but not specified further Design: prospective, parallel‐group, single centre
Participants	Number: 40 randomised Age: 20 to 70 Gender: 17 F 22 M Setting: ENT hospital department Eligibility criteria: vertigo attacks with "central signs" on ENGExclusion criteria: some medications and neurological disorders Baseline characteristics: good similarity between groups for severity, duration of disease, duration of attacks (Table 3.7.1)
Interventions	12 weeks betahistine 16 mg 3 times a day versus placebo Intervention group: n = 20 Comparator group: n = 20 Use of additional interventions: none
Outcomes	Primary outcome: intensity 5‐point ordinal scaleSecondary outcomes: patient and investigator global assessment
Funding sources	Unpublished manufacturer data
Declarations of interest	Unpublished manufacturer data
Notes	Unpublished study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)	Low risk	Randomisation list drawn up before the start of the study outside treatment centre
Allocation concealment (selection bias)	Unclear risk	Method not stated
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Double‐blind. Coding envelopes all returned unopened. Opacity not stated.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Double‐blind, but no further information
Incomplete outcome data (attrition bias) All outcomes	Low risk	Low attrition and relatively complete datasets Participants lost to follow‐up: 4
Selective reporting (reporting bias)	High risk	No data on neuro‐otological signs though these were diagnostic criteria and appear to have been assessed
Other bias	Unclear risk	—