Study of intravenous hyperalimentation: effect of selected amino acids on the stability of intravenous fat emulsions.

In an attempt to resolve the conflicts relevant to intravenous fat emulsion compatibility two amino acids, L-valine and L-histidine monohydrochloride monohydrate, were chosen as intravenous additives, and these substances were investigated as to whether they could induce significant changes in the physicochemical properties of an intravenous soybean oil emulsion. The stability of the fat emulsion was evaluated in terms of gross visual observation, particle size distribution, surface tension, pH, and the zeta potential. It was found that (a) no significant difference was produced on the particle size distribution up to 7 d after admixing, (b) the mean diameter of oil globules was approximately 0.21-0.24 micron, and (c) the fat emulsion was sufficiently stable, with a zeta potential ranging between -30 and -60 mV. The relationship of the isoelectric point (pI) of the amino acids and the pH of the buffer solutions was determined to be one of the most important factors in the stability of the fat emulsion.