Canty 1981.

Study characteristics
Methods	Allocation: no information Design: cross‐over with data extractable before cross‐over occurred
Participants	Number: 32 randomised Age: 26 to 62 Gender: 29 M and 13 F Setting: not specified Eligibility criteria: episodic vertigo of peripheral origin for at least a yearExclusion criteria: central vertigo, Ménière's, asthma, peptic ulcer Baseline characteristics: no details
Interventions	Betahistine 32 mg for 8 weeks versus placebo Intervention group: n = 15 Comparator group: n = 17 Use of additional interventions: none
Outcomes	Primary outcome: vertigo scores (4‐point ordinal scale) Secondary outcomes: caloric and oculomotor tests, adverse events
Funding sources	Not given
Declarations of interest	Not specified
Notes	Some participants in both groups had no symptoms throughout the trial duration
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", but no further information
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	Participants lost to follow‐up: 0 in first treatment phase (before cross‐over)
Selective reporting (reporting bias)	High risk	Outcome measures unclear. Also using first arm of cross‐over only. Adverse events only reported if "considered to represent adverse reactions to the study drug" without explicit criteria
Other bias	High risk	Some patients asymptomatic throughout entire trial period