The stability of ranitidine hydrochloride in various total parenteral nutrient (TPN) solutions was studied, as well as the effect of ranitidine on the stability of lipid emulsion and amino acids in these solutions. Ranitidine hydrochloride 25 mg/mL was added to each of the following mixtures to make final concentrations of approximately 50 and 100 mg/L: (1) TPN solution containing 4.5% amino acids, 22.7% dextrose, and electrolytes; (2) 10% lipid emulsion; (3) TPN solution containing 3.7% amino acids, 18.5% dextrose, 3.7% lipid emulsion, and electrolytes (all-in-one mixture); and (4) 0.9% sodium chloride injection. Mixtures were tested at room temperature and at 4 degrees C and were either protected from or exposed to fluorescent light. Sampling was done at 0, 12, 24, 36, and 48 hours, and the ranitidine concentration was determined by high-performance liquid chromatography. Samples were also analyzed for lipid particle size distribution and for amino acid content. At 48 hours, the all-in-one mixtures retained 86.0% to 91.4% of the initial ranitidine concentration. With one exception (ranitidine 50 mg/L in 0.9% sodium chloride injection, stored at room temperature and not protected from light), all other solutions retained at least 90% of the initial concentration at 48 hours. No visible changes in color and minimal changes in pH values were noted. There were no important changes in lipid particle-size distribution; 96% of all particles counted from any mixture were smaller than 1.44 microns in diameter at 48 hours. Ranitidine did not have an effect on amino acid concentrations in these mixtures.(ABSTRACT TRUNCATED AT 250 WORDS)