Reviews
A 2019 systematic review by Austin et al. of randomized controlled trials (RCTs) on topical treatments for melasma identified 35 original RCTs evaluating a wide range of approximately 20 agents. They identified cysteamine, triple combination therapy, and tranexamic acid as the products netting the most robust recommendations. The researchers characterized cysteamine as conferring strong efficacy and reported anticancer activity while triple combination therapy poses the potential risk of ochronosis and tranexamic acid may present the risk for thrombosis. They concluded that more research is necessary, though, to establish the proper concentration and optimal formulation of cysteamine as a frontline therapy.8
More reviews have since been published to further clarify where cysteamine stands among the optimal treatments for melasma. In a May 2022 systematic PubMed review of topical agents used to treat melasma, González-Molina et al. identified 80 papers meeting inclusion criteria (double or single blinded, prospective, controlled or RCTs, reviews of literature, and meta-analysis studies), with tranexamic acid and cysteamine among the novel well-tolerated agents. Cysteamine was not associated with any severe adverse effects and is recommended as an adjuvant and maintenance therapy.3
A September 2022 review by Niazi et al. found that while the signaling mechanisms through which cysteamine suppresses melasma are not well understood, the topical application of cysteamine cream is seen as safe and effective alone or in combination with other products to treat melasma.2
A systematic review and meta-analysis reported by Gomes dos Santos-Neto et al. at the end of 2022 considered the efficacy of depigmenting formulations containing 5% cysteamine for treating melasma. The meta-analysis covered six studies, with 120 melasma patients treated. The conclusion was that 5% cysteamine was effective with adverse effects unlikely.9
Baumann Cosmetic & Research Institute
Dr. Leslie S. Baumann
Cysteamine vs. hydroquinone
In 2020, Lima et al. reported the results of a quasi-randomized, multicenter, evaluator-blinded comparative study of topical 0.56% cysteamine and 4% HQ in 40 women with facial melasma. (Note that this study originally claimed a 5% cysteamine concentration, but a letter to the editor of the International Journal of Dermatology in 2020 disputed this and proved it was 0.56%) For 120 days, volunteers applied either 0.56% cysteamine or 4% HQ nightly. Tinted sunscreen (SPF 50; PPD 19) use was required for all participants. There were no differences in colorimetric evaluations between the groups, both of which showed progressive depigmenting, or in photographic assessments. The HQ group demonstrated greater mean decreases in modified melasma area severity index (mMASI) scores (41% for HQ and 24% for cysteamine at 60 days; 53% for HQ and 38% for cysteamine at 120 days). The investigators observed that while cysteamine was safe, well tolerated, and effective, it was outperformed by HQ in terms of mMASI and melasma quality of life (MELASQoL) scores.10
Early the next year, results of a randomized, double-blind, single-center study in 20 women, conducted by Nguyen et al. comparing the efficacy of cysteamine cream with HQ for melasma treatment were published. Participants were given either treatment over 16 weeks. Ultimately, five volunteers in the cysteamine group and nine in the HQ group completed the study. There was no statistically significant difference in mMASI scores between the groups. In this notably small study, HQ was tolerated better. The researchers concluded that their findings supported the argument of comparable efficacy between cysteamine and HQ, with further studies needed to establish whether cysteamine would be an appropriate alternative to HQ.11 Notably, HQ was banned by the Food and Drug Administration in 2020 in over-the-counter products.