Effect of cosurfactants on the preparation of intravenous lipid emulsions

Abstract

The stability of intravenous lipid emulsions is important for patients requiring parenteral nutrition. The use of cosurfactant is thought to improve the emulsion stability. For the emulsion preparation, the oil used were 10% and 20% soybean oil, the emulsifier were used either egg phospholipids (Lipoid® E80) alone or combined with a cosurfactant, Tween® 80, Vitamin E-TPGS or sodium oleate. The methods of preparation were varied in homogenization time, pressure and cycles through high pressure homogenizer. The formulations were sterilized by autoclaving and the physicochemical properties were investigated. The results illustrated that the formulations composed of a combination of egg phospholipids with either Vitamin E-TPGS or Tween® 80 could form the stable emulsions. The lipid emulsion containing 10% soybean oil emulsified by 1.0% egg phospholipids and 0.5% Vitamin E-TPGS was suggested due to low amount of emulsifier used and proper physicochemical properties complied with parenteral product requirements. The emulsion could remain stable for 4 weeks both at room temperature and in accelerate condition (4°C and 40°C). Its particle size (D [4,3]) of such formulation before and after autoclaving were 0.201 and 0.199 µm, respectively. The pH, osmolality and the value of zeta potential of the autoclaved emulsion after 24 hours were 6.97, 324 mOsm/kg and -41.77 mV, respectively. The pH was slightly decreased during storage while the zeta potential was increased as a function of time in all conditions. When Tween® 80 replaced Vitamin E-TPGS, the slightly larger in particle size of emulsion was observed, however the formulation still remained stable up to 4 weeks after storage at room temperature. It was concluded that the factors involved in the emulsion preparation were the process of homogenization, heat stabilization as well as the type and amount of surfactants used. The nonionic cosurfactant could improve the formation of emulsion which was stable after autoclaving and storage for at least 4 weeks by possibly the steric stabilization of the polymeric surfactant layer.