Duphar H108906NL 1990.

Study characteristics
Methods	Allocation: randomised, no further information Design: prospective, parallel‐group, single centre
Participants	Number: 100 randomised Age: mean 56 (SD 12) in intervention group, mean 53 (SD 16) in placebo group Gender: 50 F, 24 M Setting: neurology department, Netherlands Eligibility criteria: vertigo 3 times a month or chronic Exclusion criteria: other specified medical conditions and medications. Previous trial with betahistine. Baseline characteristics: data not given
Interventions	Betahistine 16 mg 3 times a day for 8 weeks Intervention group: n = 50 Comparator group: n = 50 Use of additional interventions: none
Outcomes	Primary outcome: duration of episodes in seconds, frequency of episodes per monthSecondary outcomes: patient and investigator global opinion
Funding sources	Unpublished manufacturer data
Declarations of interest	Unpublished manufacturer data
Notes	Unpublished study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	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	11 dropouts in betahistine group and 15 in placebo group; reasons unclear. Analysis was "as treated". Participants lost to follow‐up: 26.
Selective reporting (reporting bias)	High risk	Dropout data collected but not reported
Other bias	Unclear risk	—