Most subjects covered in this column are botanical ingredients used for multiple conditions in topical skin care. The focus this month, though, is a natural agent garnering attention primarily for one indication. Present in many mammals and in various cells in the human body (and particularly highly concentrated in human milk), cysteamine is a stable aminothiol that acts as an antioxidant as a result of the degradation of coenzyme A and is known to play a protective function.[1] Melasma, an acquired recurrent, chronic hyperpigmentary disorder, continues to be a treatment challenge and is often psychologically troublesome for those affected, approximately 90% of whom are women.[2] Individuals with Fitzpatrick skin types IV and V who reside in regions where UV exposure is likely are particularly prominent among those with melasma.[2] While triple combination therapy (also known as Kligman’s formula) continues to be the modern gold standard of care for melasma (over the last 30 years),[3] cysteamine, a nonmelanocytotoxic molecule, is considered viable for long-term use and safer than the long-time skin-lightening gold standard over several decades, hydroquinone (HQ), which is associated with safety concerns.[4] This month’s column is a review of recent findings on the efficacy and safety of cysteamine for the treatment of melasma.
Recent history and the 2015 study
Prior to 2015, the quick oxidation and malodorous nature of cysteamine rendered it unsuitable for use as a topical agent. However, stabilization efforts resulted in a product that first began to show efficacy that year.[5]
Mansouri et al. conducted a randomized, double-blind, placebo-controlled trial to assess the efficacy of topical cysteamine 5% to treat epidermal melasma in 2015. Over 4 months, 50 volunteers (25 in each group) applied either cysteamine cream or placebo on lesions once nightly. The mean differences at baseline between pigmented and normal skin were 75.2 ± 37 in the cysteamine group and 68.9 ± 31 in the placebo group. Statistically significant differences between the groups were identified at the 2- and 4-month points. At 2 months, the mean differences were 39.7 ± 16.6 in the cysteamine group and 63.8 ± 28.6 in the placebo group; at 4 months, the respective differences were 26.2 ± 16 and 60.7 ± 27.3. Melasma area severity index (MASI) scores were significantly lower in the cysteamine group compared with the placebo group at the end of the study, and investigator global assessment scores and patient questionnaire results revealed substantial comparative efficacy of cysteamine cream.[6] Topical cysteamine has also demonstrated notable efficacy in treating senile lentigines, which typically do not respond to topical depigmenting products.[5]
Farshi et al. used Dermacatch as a novel measurement tool to ascertain the efficacy of cysteamine cream for treating epidermal melasma in a 2018 report of a randomized, double-blind, placebo-controlled study with 40 patients. During the 4-month trial, cysteamine cream or placebo was applied nightly before sleep. Investigators measured treatment efficacy through Dermacatch, and Mexameter skin colorimetry, MASI scores, investigator global assessments, and patient questionnaires at baseline, 2 months, and 4 months. Through all measurement methods, cysteamine was found to reduce melanin content of melasma lesions, with Dermacatch performing reliably and comparably to Mexameter.[7] Since then, cysteamine has been compared to several first-line melasma therapies.
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]
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.
Cysteamine vs. Kligman’s formula
Early in 2021, Karrabi et al. published the results of a randomized, double-blind clinical trial of 50 subjects with epidermal melasma to compare cysteamine 5% with Modified Kligman’s formula. Over 4 months, participants applied once daily either cysteamine cream 5% (15 minutes exposure) or the Modified Kligman’s formula (4% hydroquinone, 0.05% retinoic acid and 0.1% betamethasone) for whole night exposure. At 2 and 4 months, a statistically significant difference in mMASI score was noted, with the percentage decline in mMASI score nearly 9% higher in the cysteamine group. The investigators concluded that cysteamine 5% demonstrated greater efficacy than the Modified Kligman’s formula and was also better tolerated.[12]
Cysteamine vs. tranexamic acid
Later that year, Karrabi et al. published the results of a single-blind, randomized clinical trial assessing the efficacy of tranexamic acid mesotherapy compared with cysteamine 5% cream in 54 melasma patients. For 4 consecutive months, the cysteamine 5% cream group applied the cream on lesions 30 minutes before going to sleep. Every 4 weeks until 2 months, a physician performed tranexamic acid mesotherapy (0.05 mL; 4 mg/mL) on individuals in the tranexamic acid group. The researchers concluded, after measurements using both a Dermacatch device and the mMASI, that neither treatment was significantly better than the other but fewer complications were observed in the cysteamine group.[13]
Safety
In 2022, Sepaskhah et al. assessed the effects of a cysteamine 5% cream and compared it with HQ 4%/ascorbic acid 3% cream for epidermal melasma in a single-blind, randomized controlled trial. Sixty-five of 80 patients completed the study. The difference in mMASI scores after 4 months was not significant between the groups nor was the improvement in quality of life, but the melanin index was significantly lower in the HQ/ascorbic acid group compared with the less substantial reduction for the cysteamine group. Nevertheless, the researchers concluded that cysteamine is a safe and suitable substitute for HQ/ascorbic acid.[4]
Conclusion
In the last decade, cysteamine has been established as a potent depigmenting agent. Its suitability and desirability as a top consideration for melasma treatment also appears to be compelling. More RCTs comparing cysteamine and other topline therapies are warranted, but current evidence shows that cysteamine is an effective and safe therapy for melasma.
Dr. Baumann is a private practice dermatologist, researcher, author, and entrepreneur in Miami. She founded the division of cosmetic dermatology at the University of Miami in 1997. The third edition of her bestselling textbook, “Cosmetic Dermatology,” was published in 2022. Dr. Baumann has received funding for advisory boards and/or clinical research trials from Allergan, Galderma, Johnson & Johnson, and Burt’s Bees. She is the CEO of Skin Type Solutions Inc., a SaaS company used to generate skin care routines in office and as an ecommerce solution. Write to her at dermnews@mdedge.com.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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Cite this: Cysteamine and Melasma - Medscape - Dec 15, 2023.
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