Stability testing of modified amino acid solutions in neonatal parenteral nutrition formulations

Context: Aqueous neonatal parenteral nutrition (PN) formulations are made up of glucose, amino acids (AAs), and electrolytes. Different AA solutions are used to make these formulations. Most licensed products do not meet the nutritional needs of preterm neonates specifically for arginine. Therefore, AA solutions with additional arginine need to be developed and proven stable before being tested for clinical efficacy. PN formulations containing modified AA solutions with 15% arginine were tested in this study. Aims: This study aims to design a stability testing protocol and assign a shelf life to the modified PN formulations being tested. Methods: Physical tests including appearance, pH, optical rotation, ultraviolet absorbance, and subvisible particle count tests as well as chemical analysis using AA assay were performed in this study. Results: Resampling of PN bag samples posed a risk for oxidation and hence single sampling of fresh PN bags for each test point is the best practice for PN stability testing trials. AA assay is a feasible method to ensure AA stability in PN formulations. Conclusion: Modified PN formulations with 15% arginine were stable for 90 days without the addition of the trace element solution. Upon the addition of trace elements, the shelf life was limited to 7 days.