BACKGROUND: Parenteral nutrition (PN) is frequently needed in neonatal intensive care. The use of standard PN has emerged as an easy-to-prescribe approach that allows one to have on-site, ready-to-use PN. The aim of this study was to test the physicochemical stability and sterility of 2 specific PN solutions as well as simulate Y-site compatibility with lipid injectable emulsions (ILE). METHODS: Our study considered 2 standard ILE-free PN solutions according to neonatal weight. These solutions were prepared in duplicate and stored at 4°C. The following physicochemical parameters were tested: visual alterations, turbidity, pH, osmolarity, and calcium concentration. Sterility was assessed by means of agar blood culture and glucose concentration determination. In addition, we assessed the stability of simulated Y-site admixtures. For each standard ILE-free PN solution, 2 3-in-1 PN admixtures were designed, considering extreme values of fluid requirements (50 and 150 ml/kg/d) and a fat supply of 2 g/kg/24 h. The physicochemical parameters tested were phase separation and fat mean droplet size distribution. RESULTS: No alterations were detected by visual inspection. Calcium concentrations, turbidity, pH, and osmolarity values remained stable in all the determinations. All agar blood cultures were negative and glucose concentration was constant over time. Physical stability of simulated Y-site admixtures was considered acceptable as mean droplet size distribution remained below 500 nm in all the emulsions. CONCLUSION: The 2 tested standard ILE-free PN solutions for neonates are physicochemically stable and sterile for 31 days under refrigeration (4°C). These solutions are also stable in case of Y-site administration with ILE at the conditions tested.