Prerovsky 1972.

Study characteristics
Methods	Study design: 2 independent, randomised, double‐blind, cross‐over, placebo‐controlled trials In the first trial, outcomes are haemodynamic, so this trial was not included The second trial is included Method of randomisation: not stated Exclusions post randomisation: none Losses to follow‐up: none
Participants	Country: Czechoslovakia Setting: research centre Number: 50 patients Age: 'adults' Gender: not stated Inclusion criteria: signs (oedema, pigmentation, post‐thrombotic syndrome) and symptoms of CVI Exclusion criteria: not stated
Interventions	Treatment: oxirutoside 1200 mg per day Control: placebo Duration: 126 days Follow‐up: 126 days
Outcomes	Primary Oedema, leg volume, pitting oedema, cellulitis Symptoms ‐ heavy legs, fatigue, pain, cramps, swelling scored by a qualitative scale (improvement, without changes, deterioration) Secondary Not stated
Notes
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "... after the administration of 3 capsules of HR (900 mg) or 3 capsules of placebo in a double blind cross‐over trial in a randomized‐order" Comment: method of randomisation not described
Allocation concealment (selection bias)	Unclear risk	Comment: no method of allocation concealment described
Blinding (patients)	Unclear risk	Comment: no information given about methods used for blinding
Blinding (study researchers)	Unclear risk	Comment: no information given about methods used for blinding
Blinding (outcome assessment)	Unclear risk	Comment: no information given about methods used for blinding
Incomplete outcome data	Low risk	Comment: number of participants described in each group, along with the most important characteristics. However, inclusion and exclusion criteria were, apart from clinical features, not well described. Adverse events and drop‐outs were well described
Selective reporting	Low risk	Comment: no protocol identified, and no differences between outcomes reported in the methods section and those reported in the results section
Other bias	Low risk	Comment: none detected