The usefulness of sugar surfactants as solubilizing agents in parenteral formulations

The usefulness of sugar surfactants as solubilizing agents was assessed and compared to commercial polyoxyethylene-based surfactants. The sugar surfactants examined comprised of monosaccharides or disaccharides with alkyl chains ranging from C(8) to C(12). Each surfactant was investigated with respect to solubilization capacity for felodipine and haemolytic activity. The haemolytic activity was determined using a static method in which surfactant solutions were added to fresh dog blood. The polyoxyethylene-based surfactants were found to be more suitable as solubilizing agents than the sugar surfactants due to better solubilization capacities combined with lower haemolytic activities. The sugar surfactants caused severe haemolysis below or at the critical micelle concentration, in contrast to the polyoxyethylene-based surfactants that are nonhaemolytic in this concentration range. The structure-related variations in haemolytic activity are probably due to variations in the surfactants partition coefficients for the distribution equilibrium between the aqueous phase and the cell membrane. Longer alkyl chains cause higher haemolytic activity, while larger saccharide groups lower the activity. The clear difference between sugar and polyoxyethylene surfactants, which are considerably less haemolytic, is due to a combination of low critical micelle concentrations and presumably low degrees of partitioning of the latter surfactants into the cell membranes.