The effect of metformin in the treatment of intractable and late onset acne: a comparison with oral isotretinoin

Background: Insulin resistance and increased insulin-like growth factor (IGF)-1 with consequent mammalian target of rapamycin complex (mTORC) 1 overexpression is responsible for acne pathogenesis, especially in women with polycystic ovary syndrome (PCOS). Metformin is shown to improve acne as an adjunct therapy in females with PCOS and males with altered metabolic profile. We evaluated the use of metformin in the treatment of resistant and late-onset acne in females, and compared it with isotretinoin. Methods: Females with late-onset acne or acne resistant to common therapies (n=70) were randomized to receive metformin (n=35) or isotretinoin (n=35) for 6 months. Changes in acne severity were scored by global acne grading system (GAGS) which was the primary outcome. Other endpoints were changes in the components of metabolic profile. Results: Six-month treatment with metformin and isotretinoin significantly reduced the GAGS from 31.9 to 24.6 and from 34.1 to 13.3, respectively, indicating the superior impact of isotretinoin. Metfromin was more effective in decreasing the GAGS score in those with PCOS (13.5±7.1 vs. 24.2±19.4, P