The stability of ranitidine hydrochloride was studied in a standard total parenteral nutrition (TPN) solution. The Canadian formulation of ranitidine hydrochloride (25 mg/mL) was added in 100-, 200-, and 300-mg doses to approximately 1200 mL of a TPN solution and allowed to stand at room temperature (23 degrees C) for seven days. During this time, samples were drawn at least once a day, and the ranitidine concentration was determined by high-performance liquid chromatography. The ranitidine concentration declined at roughly the same rate regardless of the initial concentration. During the study period, each of the three different concentrations declined to less than 70% of the initial concentration. Approximately 10% of the initial concentration was lost in 48 hours. Ranitidine hydrochloride admixtures were stable for up to 48 hours at room temperature in this standard TPN solution.