Background: Melasma is an acquired hyperpigmentation characterized by bilateral irregular brown macules and patches over sun-exposed areas of face and less commonly, forearms. No single treatment is universally effective. It has been shown that metformin could decrease intracellular cyclic adenosine mono phosphate. Since c-AMP has a role in melanogenesis, metformin can inhibit melanogenesis resulting in a significant reduction in melanin in the basal layer. Objective: The aim of the present study was toevaluate the effectiveness and safety of topical metformin for melasma treatment. Patients and methods: A quasi-experimental (pre-post comparison study) study included 30 female cases of melasma from the Dermatology outpatient clinic of Mansoura University Hospital, during the period between March 2021 and March 2022. Included females had more than 18 years old. The metformin lotion was prepared using metformin powder and a mixture of polyethylene glycol (PEG) -6; Ethylene Glycol; PEG-32, acetyl alcohol, liquid Paraffin, Methylparaben, propylparaben, and distilled water. Participants applied one layer of metformin 30% lotion on the affected area on face at night to the morning for a period of 3 months.
Results: Melasma Area and Severity Index (MASI) score decreased gradually after successive sessions (mean 13.8, 13.7, 11.5, 11.4, 11.4, respectively), with statistically significant improvement after 2, 3 months and also 1 month after the end of treatment (P values 0.002, 0.001, and 0.001, respectively). Grades of improvement significantly increased after 1, 2 months, but became stable by the 3rd month and one month after therapy. After the end of therapy, 20% of participants were satisfied, 36.7% were slightly satisfied, 26.7% were poorly satisfied, and 16.7% were not satisfied. No side effects were reported. Conclusion: Melasma was improved after using of topical metformin with no side effects appeared. Thus, topical metformin is a new, safe, and effective for melisma treatment.