Background: Acne vulgaris of adult females has increased over the past 10 years; it affects currently 20 to 30% of adult females. The physiopathology of adult female acne is distinguished from that of teenagers essentially by two factors: hormonal and inflammatory. On a therapeutic plan, in female acne, four types of systemic treatment approved in this indication include: cyclines (leading to bacterial resistance); zinc salts (less effective than cyclines); and antiandrogens (risks of phlebitis). The last alternative is represented by isotretinoin, but its use in women of childbearing potential is discouraged because of the teratogen risks.In this context, spironolactone could represent an interesting alternative. It blocks the 5-alpha-reductase receptors at the sebaceous gland and inhibits LH production at the pituitary level. It has no isotretinoin constraints and does not lead to bacterial resistance. Currently, a very few studies have been performed on a limited number of patients. They showed that at low doses (lower than 200 mg/day), spironolactone can be effective against acne.In that context, it seemed clearly interesting to perform the first double-blind randomized study of spironolactone vs cyclines, which remains the moderate acne reference treatment, and to demonstrate the superiority of spironolactone’s efficacy in order to establish it as an alternative to cyclines.Methods: Two hundred female patients will be included. They will have acne vulgaris with at least ten inflammatory lesions and no more than three nodules. After randomization, the patients will be treated by spironolactone or doxycycline for three months and after placebo. The study will be blind for the first six months and open for the last six months. Discussion: The treatment frequently used in female acne is systemic antibiotics with many courses as it is a chronic inflammatory disease. In the context of the recent WHO revelation about the serious, worldwide threat to public health of antibiotic resistance, this trial could give the physician another alternative for adult female acne before using isotretinoin, whose management is more complex. Trial registration: On ClinicalTrials.gov, registration number NCT03334682, first published on 7 November, 2017. Recruitment is still ongoing.

Background Acne vulgaris of adult woman has increased over the past 10 years; it affects currently 20 to 30% of adult women. The physiopathology of adult woman acne is distinguished from the teenager one essentially by 2 factors: hormonal one with a peripheral hyperandrogeny coupled with an hypersensibility of cutaneous androgens receptors and an inflammatory one linked with Cutibacterium acnes. On a therapeutic plan, in female acne, four types of systemic treatment, approved in this indication are: cyclines which are problematic for the bacterial resistance; zinc salts which target only the inflammatory lesions and are less effective as cycline; antiandrogens, with acetate of cyproterone associated with risks of phlebitis and pulmonary embolism and recently meningioma. The last alternative is represented by isotretinoin but the use in women of childbearing potential is binding because of the teratogen risks and in addition, peripheral hyperandrogenia represents an identified risk of relapse. In this context, the spironolactone could represent an interesting alternative. It blocks the 5-alpha-reductase receptors at sebaceous gland and inhibits LH production at the pituitary level. It has not isotretinoin constraints, does not lead to bacterial resistance and targets the peripheral hyperandrogenia. Currently, very few studies have been performed on a weak number of patients. They showed that at low doses (lower than 200mg/day), spironolactone can be effective against acne. Methods: In that context, it seemed clearly interesting to perform the first double-blind randomized study spironolactone vs cyclines, which remains the moderate acne reference treatment and to demonstrate the superiority of spironolactone’s efficacy in order to establish it as an alternative way to cyclines. Discussion: Acne’s treatment frequently used in female acne is systemic antibiotics with many courses as it is a chronic inflammatory disease. In the context of recent WHO revelation about serious, worldwide threat to public health about antibiotic resistance, this trial could permit to give to the physician another alternative in adult female acne before using isotretinoin whose management is more complex. Trial registration : On ClinicalTrials.gov, registration number NCT03334682, first published on 7 November, 2017. Recruitment is still ongoing. Keywords : acne vulgaris, spironolactone, cycline