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Abstract

Introduction: Hydroquinone (HQ), a famous anti-hyperpigmentation agent, suffers from several weaknesses such as instability due to rapid oxidation and insufficient skin penetration because of the hydrophilic structure. The aim of this research was to formulate, characterize and evaluation of in vitro skin permeability of HQ-loaded microemulsion (ME). Methods: HQ MEs were prepared by pseudoternary phase diagram method, the appropriate ratios of oil, s/c mixture, and water were chosen, and full factorial design was used with three variables at two levels for preparing eight formulations. The prepared MEs were evaluated regarding their droplet size, viscosity, pH, differential scanning calorimetry, stability, in vitro drug release, and in vitro skin permeability. Results and Discussion:The results showed that the mean droplet size range of ME samples was in the range of 7.05-79.56 nm and pH was 5.3-5.7, respectively. Viscosity range of MEs was 109-195 cps. Drug release profile showed that 90.51% of the drug released (ME-HQ-8) in the 24 h of the experiment. The kinetics of drug release from all selected MEs were approximately described by Higuchi model and showed prolonged release when compared to HQ solution. All ME formulations with different compositions and properties significantly increased flux and permeability coefficient from rat skin. J ss and Papp parameters in ME-HQ-2 formulation were 0.404 mg/cm 2 h, 0.02 cm/h, and 4 times higher than those of control, respectively. The selective MEs have 99.9% HQ amount after 6 months storage. They have visually cleared and no any color changes, thus HQ MEs can could been protect drug for a long time without antioxidant. Conclusion: The present research established that the amount of components of water, oil, and S + C in ME formulation plays an important role in the physicochemical properties and permeability parameters. This study showed that any change in content and composition of MEs could be changed physicochemical properties and permeability parameters during drug permeation from ME samples. The studied MEs increased permeation rate and permeability coefficient through rat skin. Our results were showed that ME formulation could not be increase diffusivity of HQ in stratum corneum.

Development and Ex-Vivo Skin Permeation of Sildenafil Citrate Microemulsion System for Transdermal Delivery

“…While the ME-S-7 formulation appears to be more effective in the transdermal delivery of SC, further investigation is needed. The inclusion of an optimal amount of CS, acting as a penetration enhancer, may contribute to the higher permeability of SC through the skin, as observed with SC-ME7 (29). Therefore, the reduced steady-state flux (J ss ) parameter in other formulations might result from a non-optimal amount of PG despite similar oil and water proportions.…”

“…In this study, both the J ss and the permeability coefficient through rat skin increased for all SC-ME samples. Typical enhancers can enhance the skin permeation rate of drugs by optimizing permeability parameters based on specific structural properties (29). The ME systems have shown great potential for the topical administration of therapeutic agents.…”

Transdermal Delivery of Ketorolac Tromethamine Using Microemulsion Vehicles

“…The permeability coefficient and flux from the rat skin increased significantly in all ME formulations with different features and compositions. In addition, several studies have confirmed the advantages of ME vehicles as promoters of dermal delivery (23,25), which can increase skin permeation by changing drug diffusion or partitioning coefficient (22).…”

“…According to previous studies, the S/C content in ME vehicles majorly influences the skin permeation of hydroquinone (23). Glycols (PEG400) can improve skin permeation through different mechanisms, including lipid and protein extraction, swelling of the stratum corneum, enhancing drug partitioning into the skin, and improving drug solubility in the formulation (22).…”