Stability study of azelaic acid proethosomes with lyoprotectant as stabilizer

The ethosomal carrier system can increase the penetration of azelaic acid into the stratum corneum, but ethosomes have both physical (particle aggregation or fusion) and chemical instability (chemical interaction of active ingredients during storage) that are often encountered in long-term storage. The aim of this study is to acquire proethosome formula of azelaic acid with lyoprotectant which has better stability than ethosomes of azelaic acid. Azelaic acid proethosomes were measured its absorbance using an ultraviolet-visible is spectrophotometer at a wavelength of 204 nm to obtain a percentage of entrapment efficiency (EE%). Proethosomes particle size was obtained from the analysis using particle size analyzer. Proethosomes consisting of phosphatidylcholine, ethanol, and propylene glycol were prepared by a thin-layer hydration process. After that, it was added with lyoprotectants such as trehalose, glucose, and mannitol before it was freeze-dried. Physical stability was studied with physical appearance, EE, and particle size. Chemical stability study determined the level of azelaic acid. Both tests were evaluated every 2 weeks for 8-week storage at 4°C and 27°C. Least entrapment efficiency and particle size changes was proethosomes with trehalose addition from 92.06% and 261.0 nm became 68.92% and 957.7 nm at 27°C, meanwhile at 4°C became 77.47% and 439.4 nm. While the highest percentage of azelaic acid content in proethosomes with trehalose was 62.07% (at 27°C) and without lyoprotectant 69.40%. Based on their characteristic, it can be assumed that, azelaic acid proethosomes with trehalose have the best stability than ethosomes and proethosomes with other lyoprotectants.