Carr 2001.

Methods	Double‐blind, 2‐arm, parallel‐group, randomised controlled trial, with active comparator (no placebo) and daily application for 2 weeks duration
Participants	Setting: single centre, primary care, Canada Sample size: Number randomised: 69 participants; 138 ears Number completed: 67 participants; 134 ears Participant baseline characteristics: Age: mean age 26 years Gender: not stated Inclusion criteria: patients of any age with occlusive cerumen in at least one ear Exclusion criteria: tympanic membrane perforation, ventilation tubes, mastoid cavity, otitis externa
Interventions	Intervention group (n = 35 participants; 70 ears): 10% aqueous sodium bicarbonate, ≥ 4 drops, wait 5 minutes, on a daily basis, for 14 days Comparator group (n = 34 participants; 68 ears): 2.5% aqueous acetic acid, ≥ 4 drops, wait 5 minutes, on a daily basis, for 14 days Use of additional interventions: none
Outcomes	Primary outcomes: Extent of wax clearance by average change in score for cerumen Extent of wax clearance by maximum change in scores per patient Secondary outcomes: Adverse effects Timing of measurements: After 2 weeks of ear drops
Funding sources	No information provided
Declarations of interest	No information provided
Notes	Participants lost to follow‐up: 2 participants withdrew
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Comment: randomisation by patient choice of 1 of 2 unlabelled bottles
Allocation concealment (selection bias)	Low risk	Comment: bottles were prepared by pharmacy and were unmarked except for A or B; un‐blinding occurred only at end of study
Blinding of participants and personnel (performance bias) All outcomes	High risk	Comment: the odour of acetic acid was detected by participants
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Comment: examiners were blinded and were unable to detect the smell of acetic acid
Incomplete outcome data (attrition bias) All outcomes	Low risk	Comment: all participants were accounted for; 2 participants withdrew, with reasons described
Selective reporting (reporting bias)	Low risk	Comment: all outcomes proposed in the methods were reported in the results
Other bias	Low risk	Comment: no further sources of bias identified