Hydroquinone Hydroxypropyl-β-cyclodextrin Inclusion Complex Based Topical Cream as an Effective Treatment of Melasma by Releasing Hydroquinone in a Controlled Manner

Objective Hydroquinone (HQ) is globally regarded as the gold-standard topical agent for melasma treatment. However, its clinical utility is limited by several challenges: susceptibility to oxidation induced by light, air, and metal ions, which generates harmful byproducts and triggers adverse effects (e.g., skin irritation, pruritus, and dermatitis). Moreover, excessively high concentration in the skin of hydroquinone due to the burst release of HQ may cause melanocyte cytotoxicity, while systemic penetration raises additional safety concerns. To overcome these limitations and enhance the therapeutic applicability of HQ, this study aims to develop strategies that mitigate its instability and optimize its delivery profile. Methods In this study, an oil-in-water cream containing hydroquinone cyclodextrin inclusion complex (HQ-HPCD) was designed with PO as the oil phase matrix to improve the treatment of melasma. Results As expected, the in vitro release profile of HQ-HPCD cream exhibited near-zero-order kinetics, effectively mitigating the irritation associated with burst release-induced peak concentrations. The HQ-HPCD inclusion complex demonstrated enhanced photostability and oxidative resistance compared to free HQ. Then it was confirmed by B16F10 cells that the HQ-HPCD increased the IC 50 of HQ by 4.6 times. Moreover, skin condition, tyrosinase activity, SOD (Superoxide Dismutase), MDA (Malondialdehyde) and melanin content in the mice were detected and the results were in line with the in vitro assays, which showed that PO-HQ-HPCD cream has higher resistance to melanin deposition and lower irritation. Conclusions This study successfully developed a topical formulation that enhances the stability of hydroquinone (HQ) while achieving its sustained release in the epidermal layer, thereby improving its clinical applicability of melasma.