Abstract: 【Abstract】 Objective To explore the clinical efficacy and safety of nano-microneedles in the treatment of melasma with tranexamic acid. Methods A total of 80 patients with chloasma who were treated in the Department of Dermatology, Guangzhou Dermatology Hospital from March 2023 to May 2024 were randomly divided into nano-microneedle group (nano-microneedle introduced tranexamic acid) and ultrasound group (ultrasound introduced tranexamic acid), with 40 cases in each group. Both groups were treated once a week for a total of 8 times. Two independent sample t test, rank sum test and chi-square test were used for statistical analysis. Results After 12 weeks of treatment, the MASI scores of the two groups were lower than those before treatment. The median MASI score of the nano-microneedle group [5.80 (4.20, 9.35)] was lower than that of the ultrasound group [8.65 (5.70, 10.80)], and the difference was statistically significant (Z=2.50, P=0.012).The total effective rate of nano-microneedles group (97.5%, 39/40) was higher than that of ultrasound group (55.0%, 22/40), and the difference was statistically significant (?2 = 19.95, P < 0.001). The left and right facial VISIA brown spot scores of the nano-microneedle group (126.18±36.54, 138.50±40.76) were lower than those of the ultrasound group (142.37±32.40, 157.13±39.59), and the difference was statistically significant (t=-2.10, -2.07; P=0.039, 0.041). The pain score of the nano-microneedle group was（4.12±1.47）.The patients in the nano-microneedle group had different degrees of adverse reactions such as erythema, edema and dryness after operation, which were all relieved within 48 hours. No adverse reactions were observed in ultrasound group. Conclusion Nano-microneedle tranexamic acid has significant clinical efficacy and good safety in the treatment of melasma, which provides more options for the treatment of melasma.

Key words: Chloasma, Therapy, Tranexamic acid, Nanomicroneedles, Ultrasonic induction, Nanocrystalline microneedles, Transdermal drug delivery