Stability of nizatidine in total nutrient admixtures

The stability of nizatidine in total nutrient admixtures (TNAs) and the effect of the drug on the stability of lipid emulsions in the TNAs were studied. Duplicate 1476-mL amino acid-dextrose base solutions were prepared; nizatidine 300 mg was added to one. TNAs were prepared by adding to 75-mL samples of the base solutions Intralipid (KabiVitrum) or Liposyn II (Abbott) and sterile water as needed to achieve final lipid concentrations of 3% and 5%. Triplicate 100-mL samples for each lipid product and concentration were prepared; fat-free samples containing nizatidine were also studied. The theoretical final nizatidine concentration was 150 micrograms/mL. Samples were stored at 22 degrees C for 48 hours. Initially and at 12, 24, and 48 hours, the samples were visually inspected, tested for pH and particle-size distribution, and assayed by high-performance liquid chromatography for nizatidine concentration. No color change, precipitation, creaming, or oiling out was noted. For the 12 TNAs containing nizatidine, mean solution pH during the study was 5.88; stability of the lipid products requires pH values greater than or equal to 5.5. Particle-size distribution did not differ appreciably between the nizatidine-containing and drug-free TNAs. Nizatidine concentrations remained greater than 90% of the initial concentration. Nizatidine at a theoretical concentration of 150 micrograms/mL was stable for 48 hours at 22 degrees C in TNA solutions containing 3% and 5% Intralipid or Liposyn II and did not appear to affect lipid emulsion stability.