The stability of amikacin, gentamicin, and tobramycin in total nutrient admixtures

Amikacin (A), gentamicin (G), and tobramycin (T) were added to eight different total nutrient admixtures (TNA) with varying concentrations of dextrose, amino acid, and fat emulsion to determine drug and emulsion stability. All TNA were prepared aseptically and stored at room temperature under normal room lighting for 12 hr before drug addition. One volume of each drug was added to an equal volume of each of the eight TNAs to simulate 1:1 piggyback contact volumes. Samples were left at room temperature for 6 hr. Drug concentrations were analyzed by fluorescence polarization immunoassay. TNA/drug admixtures were pH tested and visually inspected before and after centrifugation in microhematocrit tubes, noting signs of emulsion stability at 1 and 6 hr. Emulsion particle size was determined at 1 and 6 hr using interference contrast microscopy. All three drugs retained their immunoreactivity in all TNAs for at least 6 hr. G and T were stable in all eight TNAs for at least 6 hr with no significant effect on emulsion particle size or stability after centrifugation. A was incompatible with all eight TNAs, resulting in visual breaking of all emulsions within 1 hr. Therefore, G and T, but not A, can be administered via piggyback method with the eight TNAs tested if the infusion is completed within 6 hr.