Conraux 1988.

Study characteristics
Methods	Allocation: not reported Design: prospective, parallel comparison
Participants	Number: 57 randomised Age: not given Gender: not given Setting: multicentre Eligibility criteria: chronic vertigo for at least 3 months; 6 attacks in preceding 2 monthsExclusion criteria: anti‐vertigo drugs and other relevant medications Baseline characteristics: baseline group comparable for average intensity but otherwise baseline comparability unclear
Interventions	Betahistine up to 48 mg per day for 3 months versus placebo Intervention group: n = 27 Comparator group: n = 20 Use of additional interventions: none
Outcomes	Primary outcome: number of patients who improve with respect to vertigo symptoms Secondary outcomes: 5‐point ordinal scale for intensity, patient and physician global assessment
Funding sources	Not given
Declarations of interest	1 co‐author affiliated to manufacturer
Notes	"No difference" in adverse effects
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	High risk	Participants lost to follow‐up: 10. Unclear which groups they belonged to. Analysis is "as treated".
Selective reporting (reporting bias)	High risk	Most outcomes not given as raw data or measures of spread missing
Other bias	Unclear risk	—