Mixing glycolic acid with retinaldehyde: RALGA, a technical achievement

Background: The use of retinaldehyde or glycolic acid was found to be effective in topical acne treatments. Objective: The aim of this study was thus to take advantage of the possible synergistic effect between retinaldehyde and glycolic acid and to combine the latter in a single formulation, in other words, in an oil-in-water emulsion. Methods: A certain number of critical parameters were taken into account when designing the formulation, i.e. solubility of retinaldehyde and glycolic acid, pH of the finished product and insufficient stability of retinaldehyde notably in the presence of water. Consequently, the oil components, which form the oily phase of the emulsion, were carefully selected according to the solubility of retinaldehyde. Moreover, we aimed at obtaining adequate emulsion stability so that a large amount of water could be used to make the hydroxy acid soluble. Results and Conclusion: The best retinaldehyde-glycolic acid ( RALGA) formulation developed had a low pH ( around 3.5) and, when stored at 40 C, revealed a good stability. Finally, the antibacterial activity of this formulation was also tested in vitro against Propionibacterium acnes and showed antibacterial results after only 5 min of contact. Copyright (C) 2005 S. Karger AG, Basel