Design of an Ante-enhancer with an Azone-Mimic Structure using Ionic Liquid

Design of Ionic Liquid Formulations with Azone-Mimic Structures for Enhanced Drug Skin Permeation

Although laurocapram (Azone) significantly enhances the skin permeation of drugs, its development was hindered by its skin irritation. We then developed an Azone-mimic ionic liquid (IL-Azone), composed of less irritating cationic ε-caprolactam and anionic myristic acid. IL-Azone dissociates to the original cation and anion in the presence of water in the formulation. We tried to select a formulation suitable for IL-Azone in the present study. Each formulation contained 5 % of either Azone or IL-Azone along with the model drug antipyrine, and skin permeation experiments of the drug were conducted. The results revealed that IL-Azone did not enhance skin permeation when combined with most formulations tested. However, a notable and rapid enhancement in skin permeation was observed when combined with white petrolatum. This effect could be attributed to the minimal water content in white petrolatum, which prevented IL-Azone degradation. Furthermore, its permeation-enhancing effects from IL-Azone in white petrolatum were more pronounced and rapid than Azone. The rapid onset observed with IL-Azone can be attributed to its degradation into its original components at the interface between the stratum corneum and the living epidermis, which results in a shorter lag time before achieving a steady-state concentration in the SC compared to Azone.

Enhanced Physical Stability of L-Ascorbic Acid in an Ionic Liquid

Ionic liquid (IL) technology was used to enhance the stability of L-ascorbic acid (AA). Pyridoxine was selected as the counter cation for anionic AA in IL. After AA was dissolved in water at 40 °C, its ratio decreased to 3.2% after 7 d. In contrast, the IL formulation showed negligible degradation, with almost no loss of AA even after 28 d. These results suggest that the use of IL enhances the stability of AA.