title: Mixing glycolic acid with retinaldehyde: RALGA, a technical achievement.
abstract: 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.
  
  
  CONCLUSIONS
  The best retinaldehyde-glycolic acid (RALGA) formulation developed had a low pH (around 3.5) and, when stored at 40 degrees 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.
authors.affiliation: Pierre Fabre Dermo-Cosmétique, Castanet-Tolosan, France. pascal.bordat@pierre-fabre.com
authors.forename: P
authors.initials: P
authors.lastname: Bordat
authors.forename: S
authors.initials: S
authors.lastname: Chesnoy
mesh_terms: D002626:Chemistry, Pharmaceutical; D003879:Dermatologic Agents / Q000737:chemistry*; D004338:Drug Combinations; D015195:Drug Design; D004357:Drug Synergism; D004655:Emulsions; D006016:Glycolates / Q000737:chemistry* / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007641:Keratolytic Agents / Q000737:chemistry*; D011425:Propionibacterium acnes / Q000187:drug effects; D012172:Retinaldehyde / Q000737:chemistry* / Q000494:pharmacology; D012995:Solubility
chemical_list: D003879:Dermatologic Agents; D004338:Drug Combinations; D004655:Emulsions; D006016:Glycolates; D007641:Keratolytic Agents; C501639:diacneal; C031149:glycolic acid; D012172:Retinaldehyde