In vitro studies of the hemolytic activity of microemulsions in human erythrocytes

Hemolytic activity in human erythrocytes as alternative to in vivo testing was used as a potential screening method to evaluate irritant potential of microemulsions for possible application in pharmaceutical and cosmetic formulations. Microemulsions were prepared by mixing surfactants and oil and slowly titrating the mixtures with aliquots of phosphate buffer saline or water. All microemulsions were characterized by dynamic light scattering to determine both the mean droplet size and droplet distribution. Microemulsion droplet size decreased as aqueous component increased. No differences in droplet size were observed between formulations containing phosphate buffered saline or water. The hemolytic activity was measured photometrically by the RBC assay, based in the cell membrane lysis, to estimate the potential irritation of both surfactants and microemulsions selected with water or PBS as aqueous component. The most hemolytic microemulsions corresponded to those containing the surfactant Labrasol®, with or without butyl lactate, and no differences were found between the hemolytic activity between these components and microemulsions containing them. The highest hemolytic activity of microemulsions in this study may be attributed to the excipient used in the formulations. We should avoid the use of high amounts of Labrasol® and butyl lactate in microemulsions because they may be potential irritants.