Formulation and stability aspects of new lipid emulsions for parenteral nutrition (PN) Gil Hardy Faculty of medical and Health Sciences, University of Auckland, Auckland, New Zealand Intravenous lipid emulsions (IVLE) are an essential component of PN regimens and are increasingly utilised in All-IN-One (AIO) admixtures. IVLE contain soyabean long chain triglycerides (LCT), with or without olive, coconut or fish oils. Traditional LCT emulsions are mixtures of n-6 polyunsaturated fatty acids (PUFA) and long chain saturated fatty acids (SFA). Newer emulsions comprise either a mixture of n-6 PUFA and n-9 mononunsaturates (MUFA) from olive oil, or a 1:1 ratio of LCT with medium chain triglycerides (MCT). Fish oil emulsions are predominantly n-3 PUFA, but lack essential fatty acids and are formulated to supplement other IVLE or are manufactured as a ‘multi-oil’ combination of soya, medium chain, olive and fish oils (SMOF). Lipid peroxidation is a free radical-initiated process leading to deterioration of PUFA, which constitute 50% of total lipids in traditional emulsions. IVLE undergo photooxidation to produce lipid peroxides (LPX) within 24 hours after addition to a PN admixture, but a major scavenger for LPX is d- +-tocopherol, which breaks the chain reaction. New IVLE with +- tocopherol and lower content of pro-inflammatory SFA and n-6 PUFA, make them more resistant to peroxidation. Thus premature babies and long term PN patients exhibit lower serum LPX values after therapy with olive oil based lipid containing only 20% PUFA. Particle size distribution (PSD) of AIO ensure large particles do not lead to pharmaceutically unstable admixtures. AIO compounded with traditional soy-based emulsions generally have higher PSD than those admixtures produced with coconut or olive oil based lipids. The new IVLE have more physiological formulations with improved stability profiles and appear less immunosuppressive and may inhibit release of pro-inflammatory cytokines. These observations offer exciting possibilities to deliver pharmaconutrients safely, efficiently and more efficaciously via lipid-based PN.   From PENSA 2009 “Energizing Nutrition Support Practice for Life” June 5-7 2009, Shangri-La Hotel, Kuala Lumpur, Malaysia Page: 29