Novel dissolving microneedles preparation for synergistic melasma therapy: Combined effects of tranexamic acid and licorice extract.

The aim of this study was to prepare dissolving microneedles (DMNs) patches containing tranexamic acid (TA) for the treatment of melasma. Polyvinyl alcohol (PVA) and polyvinylpyrrolidone (PVP) were preferred as matrix materials through the compatibility experiment. In the in vitro permeation study, the transdermal amount of TA was significantly promoted through dissolving microneedles with the cumulative release was 44.43 ± 6.55%. By comparison, the release of TA solution assisted with solid microneedles (SMNs) was merely 11.31 ± 2.30% (p < 0.05). Pharmacokinetics study indicated the bioavailability of dissolving microneedles was more than 1.3 times compared with oral administration. In pharmacodynamics investigation, TA dissolving microneedles obviously reduced melanin deposition in the skin of melasma guinea pigs after 8 consecutive administrations. In particular, the combination of tranexamic acid and licorice extract (LIC) dissolving microneedles worked better than tranexamic acid alone. Accelerated stress conditions including high temperature, high humidity, as well as photostability were designed to prove that TA microneedles maintained good pharmaceutical stability. In conclusion, tranexamic acid dissolving microneedles showed reliable quality and remarkable effect. Moreover, the combination of tranexamic acid and licorice extract had a synergistic therapy in melasma.