Efficacy of Metformin for the Treatment of Melasma: A Systematic Review and Meta-analysis of Randomised Controlled Trials
Abstract
Melasma is a chronic, relapsing hyperpigmentation disorder that remains difficult to treat with conventional therapies. Emerging evidence suggests that metformin, beyond its glucose-lowering effects, may exert dermatologic benefits through anti-inflammatory and anti-melanogenic mechanisms. This systematic review and meta-analysis evaluated the efficacy of metformin in melasma management through comprehensive searches of PubMed, Scopus, Web of Science, and Cochrane Library to identify randomized controlled trials (RCTs) investigating metformin for melasma conducted between January 2019 and January 2025. Data were independently extracted, and pooled analyses were performed using a random-effects model in RevMan (version 5.1.0). The primary outcome was change in the Melasma Area and Severity Index (MASI), with secondary outcomes including patient satisfaction. Four RCTs met inclusion criteria. Metformin significantly reduced MASI scores versus placebo (SMD = –1.07; 95% CI [–1.54, –0.60];
P
< 0.001), with moderate, non-significant heterogeneity (I² = 52%). Patient satisfaction favored metformin, with more participants reporting being “very satisfied” (RR = 14.88; 95% CI [2.06, 107.47];
P
= 0.007; I² = 0%). Reports of “partial satisfaction” were significantly lower with metformin (RR = 0.34; 95% CI [0.15, 0.78];
P
= 0.01), while “moderate satisfaction” did not differ significantly (RR = 1.07; 95% CI [0.52, 2.23];
P
= 0.85). This systematic review and meta-analysis demonstrated…
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