Bojar 1994.

Study characteristics
Methods	Aim of study: This double‐blind study was carried out to assess the ability of 4% w/v erythromycin with and without 1.2% w/v zinc acetate to reduce the numbers of erythromycin‐resistant propionibacterium in vivo, and also to monitor the acquisition of resistant strains de novo during therapy Design: parallel, active‐control Unit of allocation: individuals Allocation: randomised; no further detail Blinding: double‐blind Duration of trial (from recruitment to last follow‐up): not described Dropouts: 7 in total
Participants	Population description: mild to moderate AV (grades 0.5 to 3.0 on the Burke and Cunliffe Scale) Setting: not described Randomised number: 52 Age (years): treatment group: 17.9 years, 13 to 27 years; control group: 20.4 years, 15 to 37 years Sex (M/F): 30/15 in both groups Severity of illness: mild to moderate
Interventions	Name of treatment group: erythromycin with zinc acetate n = 20 (number of participants completed the study, number of randomised participants was unknown) Description: topical 4% w/v erythromycin with 1.2% w/v zinc acetate, in a base consisting of 26% w/v di‐isopropyl sebacate and 57% w/v ethanol. Applied with a plain soap for skin cleansing Treatment period: 12 weeks Timing: twice daily Name of treatment group: erythromycin n = 25 (number of participants completed the study, number of randomised participants was unknown) Description: topical 4% w/v erythromycin, in a base consisting of 26% w/v di‐isopropyl sebacate and 57% w/v ethanol. Applied with a plain soap for skin cleansing Treatment period: 12 weeks Timing: twice daily
Outcomes	Primary outcomes Participants' global self‐assessment of acne improvement (e.g. measured by a 4‐point scale: excellent, good, fair, and poor). Authors did not report this outcome Withdrawal for any reason. 7 in total, unknown in each group Secondary outcomes Change in lesion counts (total or inflamed and non‐inflamed separately). Baseline and week 4, 8 and 12. Authors only reported no difference between groups without P value and other summary statistics Physicians' global evaluation of acne improvement. Authors did not report this outcome Minor adverse events (assessed as total number of participants who experienced at least one minor adverse event). Authors did not report this outcome Quality of life. Authors did not report this outcome. Other outcomes that were not analysed in this review Microbiological evaluations
Notes	Funding Brocades Pharma for financial support
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Patients were randomly allocated to treatment with either...". Comment: no details of random methods were described
Allocation concealment (selection bias)	Unclear risk	We judged an unclear risk of bias because the authors did not report this issue.
Blinding of participants and personnel (performance bias) All outcomes	Unclear risk	Although 'double‐blind' was mentioned, no details were reported for its identification.
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Although 'double‐blind' was mentioned, no details were reported for its identification.
Incomplete outcome data (attrition bias) All outcomes	High risk	Quote: "Seven of the original 52 patients failed to attend one or more follow‐up appointments, and have been excluded from the data analysis". Comment: the author did not report which of the seven participants belonged to which group, number of missing data considered enough to introduce bias
Selective reporting (reporting bias)	High risk	"Side effects" not reported
Other bias	Low risk	No other potential bias identified