Otto 2008.

Study characteristics
Methods	Allocation: computer‐generated randomisation Design: parallel‐group
Participants	26 with vertigo as part of "vertebrobasilar ischaemia" (see below, clinical diagnosis) Number: 26 randomised, 22 analysed Age: 31 to 70 Gender: (M:F) 7:19 Setting: ENT clinic, Germany Eligibility criteria: vertigo with at least 2 of impaired hearing, impaired vision, tinnitus, headache ("vertebrobasilar ischaemia" according to authors), 2 weeks off anti‐vertigo drugsExclusion criteria: other causes of vertigo, other medical conditions (specified) Baseline characteristics: baseline female predominance in placebo group
Interventions	Betahistine 12 mg 3 times a day versus placebo for 4 weeks Intervention group: n = 13 Comparator group: n = 13 Use of additional interventions: none, but study also included a third group treated with fixed combination of cinnarizine and dimenhydrinate, which was the main intervention of interest to the study authors
Outcomes	Primary outcome: vertigo scores (4‐point scale)Secondary outcomes: overall efficacy rated by both patients and investigator on a 5‐point scale
Funding sources	Not stated
Declarations of interest	1 co‐author affiliated to manufacturer
Notes	Study was designed to compare betahistine and placebo with a third comparator group (fixed proprietary combination of dimenhydrinate and cinnarizine). Only the betahistine/placebo comparison is included in this review
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Computer‐generated randomisation
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	15% lost to follow‐up in each group Participants lost to follow‐up: 4
Selective reporting (reporting bias)	High risk	Study was designed for a different purpose (assessment of the effect of a different drug)
Other bias	Unclear risk	—