Legent 1988.

Study characteristics
Methods	Allocation: randomised, but no further information Design: parallel‐group
Participants	Number: 81 Age: not specified Gender: not specified Setting: ENT departments, France Eligibility criteria: progressive episodic vertigo with or without cochlear symptomsExclusion criteria: central vertigo, BPPV, tumours, CNS disease, iatrogenic, ear disease, pregnancy, psychiatric disease, asthma, gastrointestinal disease Baseline characteristics: betahistine group slightly lower intensity and longer duration of attack scores; raw data not given
Interventions	Betahistine 16 mg 3 times a day for 3 months versus placebo n = 59 in total in analysis, but unclear how many in each group (intervention/comparator) Use of additional interventions: none
Outcomes	Primary outcome: proportion of patients with "good results"Secondary outcomes: intensity (5‐point scale), duration and frequency of attacks, global patient/doctor rating
Funding sources	One co‐author affiliated to manufacturer
Declarations of interest	One co‐author affiliated to manufacturer
Notes	Groups "similar at baseline" clinically but data not given
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	Unclear risk	Double‐blind; no further information
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Double‐blind; no further information
Incomplete outcome data (attrition bias) All outcomes	High risk	Participants lost to follow‐up: 22. Numbers lost in each treatment arm unclear.
Selective reporting (reporting bias)	High risk	Raw data for outcomes missing, e.g. patient and investigator satisfaction
Other bias	Unclear risk	—