Gollnick 2004b.

Study characteristics
Methods	Aim of study: to clinically test 15% AZA gel against 1% clindamycin gel in participants with mild to moderate AV Design: parallel, double‐blind, randomised, multicentre, phase III trial Unit of allocation: patients Allocation: randomisation; no details Blinding: double‐blinded study; no details Duration of trial (from recruitment to last follow‐up): 1997 to 2000 Dropouts: 5 participants in the AZA group and 1 participant in the clindamycin group discontinued the study due to adverse events. 20 participants in the AZA group and 10 participants in the clindamycin group did not complete the scheduled 4 months treatment.
Participants	Population description: mild to moderate AV Setting: multicentres, recruitment in Germany, Netherlands, Norway, and Greece Randomised number: 229; 114 to azelaic group and 115 to clindamycin group Age, median years (range): AZA group: 19 (14 to 50); clindamycin group: 19 (13 to 38) Sex, numbers male/female (% male): AZA group: 47/67 (41%); clindamycin group: 55/60 (48%) Severity of illness: mild to moderate
Interventions	Name of treatment group: AZA group, N = 114 Description: 15% AZA in hydro gel (brand: Skinoren 15% Gel) topical application 2 times per day for 4 months Treatment period: 4 months Timing: 2 times per day Name of control group: clindamycin group, N = 115 Description: 1% clindamycin in hydro gel (brand: Basocin Acne Gel) topical application 2 times per day for 4 months Treatment period: 4 months Timing: 2 times per day
Outcomes	Primary outcomes Participants' global self‐assessment of acne improvement (e.g. measured by a four‐point scale: excellent, good, fair, and poor). Week 16; a four‐point Likert‐type rating scale (very good, good, moderate, poor) Withdrawal for any reason (30 withdrawals during the 4 months treatment) Secondary outcomes Change in lesion counts (total or inflamed and non‐inflamed separately). Reported median of percent reduction of the lesions, week 16 Physicians' global evaluation of acne improvement. Week 16; a four‐point Likert‐type rating scale (very good, good, moderate, poor) Minor adverse events (assessed as total number of participants who experienced at least one minor adverse event). Adverse drug‐related events Quality of life. Authors did not report this outcome.
Notes	Funding: not reported; two authors were employees of the pharmaceutical company Schering
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Although 'randomised' was mentioned, no details were reported for random sequence generation.
Allocation concealment (selection bias)	Unclear risk	No details of allocation concealment were described.
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	Number of participants continuously dropped out, which is shown in Table 2 for the time points 1, 2, 3, ≥ 4 months from 100% down to 83%. Six participants dropped out possibly because of minor local adverse events. Number of missing data considered enough to introduce bias
Selective reporting (reporting bias)	High risk	Additionally reported outcome (Subjective global evaluations) that were not mentioned in the Method section
Other bias	Unclear risk	Minor local adverse events were compared between Gollnick 2004a and Gollnick 2004b in an indirect fashion. In study 2, the duration of therapy differed between test and control arm. An advantage was reported for AZA, although the difference was not significant. Conflict of interest: authors are employees of a pharmaceutical company that marketed AZA