Oosterveld 1989.

Study characteristics
Methods	Allocation: randomised, but no further information Design: cross‐over with data extractable before cross‐over
Participants	Number: 114 randomised Age: < 65 years old Gender: 46 F, 36 M Setting: 18 ENT practices in the Netherlands Eligibility criteria: episodic vertigo, at least 2 episodes of vertigo in the last month Exclusion criteria: vertigo secondary to middle/inner ear infection, Parkinson's, brain tumour, head trauma, epilepsy, multiple sclerosis or ocular diseases Baseline characteristics: baseline duration is longer in the placebo group
Interventions	Betahistine 16 mg 3 times a day for 10 weeks (5 weeks prior to cross‐over) Intervention group: n = 38 analysed Comparator group: n = 44 analysed Use of additional interventions: none
Outcomes	Primary outcome: frequency, duration, severity of attacks (4‐point scale)Secondary outcomes: global rating by patient, unwanted signs and symptoms
Funding sources	Not reported
Declarations of interest	Not reported. Pharmaceutical company assisted with preparation of report.
Notes	—
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	32 missing/excluded; unclear from which groups some of them originate Participants lost to follow‐up: 32
Selective reporting (reporting bias)	Low risk	Appropriate outcomes reported
Other bias	Unclear risk	—