The stability of famotidine in two types of total nutrient admixtures (TNAs), one containing 5% intravenous fat emulsion of long-chain triglycerides and the other, of medium- and long-chain triglycerides, was studied. The TNAs, which contained lipids, glucose, amino acids, electrolytes, vitamins, and trace elements, were prepared aseptically in ethylene-vinyl acetate containers. Famotidine 40 mg was added to both types of TNAs and famotidine 80 mg was added to both types to yield concentrations of 20 and 40 mg/L (expressed hereafter as micrograms per milliliter), respectively. A control solution was prepared for each type of TNA. Samples were removed at 0, 12, 24, 48, and 72 hours for measurement of pH and of famotidine concentration by high-performance liquid chromatography; the solutions were visually inspected for color changes, creaming, and formation of precipitates. Particle size distributions were measured at 72 hours and compared with those for the control solutions at time zero. No appreciable changes in pH occurred over 72 hours, and no physicochemical changes were observed. Famotidine 20 and 40 micrograms/mL was stable for at least 72 hours in both types of TNAs. There was no variation in particle size distribution. Famotidine appears to be stable for up to 72 hours at room temperature in the TNAs studied, and it appears not to alter the integrity of the two lipid emulsions.