Bayer 2011.

Methods	Multicenter trial conducted in China from 2008 to 2010 Double‐blind (subject and investigator) No information on how the randomization schedule was generated.
Participants	179 women, 14 to 45 years old. Inclusion criteria: >1 year post‐menarche with moderate acne vulgaris with no contraindication to COCs; healthy except for moderate acne; smokers up to age 30 (inclusive). Exclusion criteria: pregnancy, lactation (< 3 menstrual cycles since delivery, abortion, or lactation); obesity (Body Mass Index > 30 kg/m2); hypersensitivity to ingredient of study drug; any disease or condition that may worsen under hormonal treatment
Interventions	Group 1: Drospirenone (DRSP) 3 mg plus EE 20 µg Group 2: Placebo Duration: 6 cycles
Outcomes	Primary: percent change in total lesion count in full analysis and per‐protocol analysis. Secondary: percentage of participants classified as "0" (clear) or "1" (almost clear) on 6‐point ISGA (Investigator Static Global Assessment); percent change in inflammatory and non‐inflammatory lesion counts; percent change in lesion counts of papules, pustules, nodules, open comedones, and closed comedones; percentage of participants classified as 'improved' according to investigator's and participant's overall ratings. Improvement in lesion count is indicated by larger percent change: ((count at baseline ‐ count at cycle 6)/ count at baseline)*100
Notes	Results were posted on ClinicalTrials.gov Study was sponsored by Bayer Schering Pharma Excluded after randomization 6 women who did not take study drug (2 DRSP and 4 placebo) Lost to follow up: DRSP 4/89 (4.5%); placebo 6/90 (6.7%).
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	No information