Efficacy of metformin vs. doxycycline in treating acne vulgaris: An assessor-blinded, add-on, randomized, controlled clinical trial

Abstract

Introduction: Insulin-like growth factor 1 (IGF-1) plays a role in the pathogenesis of acne vulgaris. Metformin can reduce IGF-1 levels and insulin resistance, so it may be useful in treating acne. Objective: This study compared the efficacy of metformin and doxycycline in treating patients with acne vulgaris. Methods: In this assessor-blind, add-on, randomized controlled clinical trial, we enrolled 40 patients with moderate acne vulgaris aged 15–40 and randomly divided them into two groups. For two months, the first group received doxycycline 100 mg capsules daily, and the second received metformin 500 mg tablets twice daily. The patients in both groups were adminitered to apply a fingertip (fourth finger) of 5% benzoyl peroxide gel (Pangel®) topically every night over the lesions, and to wash it off after 30 min. Patients were evaluated using the Global Acne Grading System (GAGS) score, Investigator Global Assessment for Acne (IGA) score, Cardiff Acne Disability Index (CADI), Total Acne Lesion Count (TLC), and the number of inflammatory and noninflammatory lesions. Results: By the end of the study, the GAGS, IGA, CADI, and TLC scores and the number of inflammatory and noninflammatory lesions decreased significantly in both groups (p < 0.001), with no significant difference between the two groups (p > 0.05). Conclusion: This trial indicates equal efficacy of doxycycline and metformin in reducing acne vulgaris severity, with doxycycline performing better in reducing lesions of the inflammatory type. Confirmatory or equivalence clinical trials should be performed to confirm our results.