Lecithin parenteral nutrition

Typical solid lipids used are glycerides and/or fatty acids, and may constitute 30% of the formulation. These are from the same family of lipids found in parenteral nutrition emulsions, such as Intralipid, which have been successfully administered intravenously for several decades. Typical excipients are Dynasan 112, composed of short chain fatty acids, Compritol, lecithin, used as an emulsifier, and surfactants such as polysorbate 80, polaxamer 188, PVP, bile salts such as sodium glycocholate, and Span 85. Water can be replaced with oils or PEG 600 to yield dispersions which can be filled into soft gelatin capsules. 

Lecithins are mainly used in pharmaceutical products as dispersing, emulsifying, and stabilizing agents and are included in intramuscular and intravenous injections, parenteral nutrition formulations, and topical products such as creams and ointments. 

Lecithins are also used in suppository bases, to reduce the brittleness of suppositories, and have been investigated for their absorption-enhancing properties in an intranasal insulin formulation. Lecithins are also commonly used as a component of enteral and parenteral nutrition formulations. 

Therefore, micelle-forming surfactant molecules (e.g., SDS) will be present in three different forms, namely, on the lipid surface, as micelles, and as monomeric surfactant molecules in solution. Lecithin will form liposomes, which have also been detected in nanoemulsions for parenteral nutrition [77], Mixed micelles have to be considered in glycocholate/lecithin-stabilized and -related systems. Micelles, mixed micelles, and liposomes are known to solubilize drugs, and are therefore attractive alternative drug-incorporation sites (especially with respect to the low incorporation capacity of lipid crystals). 

The consequence.s arising from these new (rfjservations are considerable. EHie to the free phospholipid in fat emulsions used for parenteral nutrition there is an inciea.se in serum cholesterin level (5) and abnormal lipoproteins are formed (61.115). Both of these phenomena are more pronounced with 10 emulsions that have a higher amount of free phospholipid. As a result of these findings in the meantime emulsion.s are being produced that are stabilized with less lecithin (0.6-0.895 M19). 

To. summarize For autoclaving, nanosuspensioms need preferentially to he stabilized by charged emulsifiers such as lecithin (Phospholipon). Similar to fat emulsions for parenteral nutrition, which are also stabilized by iecUhin. nanosuspensions can withstand the sterilization procedure. 

For intravenous or intramuscular administration, oil-soluble actives can be formulated as an oil-water-emulsion. When administered intravenously it is essential that the droplet size is about the same size as the lipid particles that circulate in the blood, the chylomicrons (0.2-3 pm). A typical emulsion contains 10-20 % soybean oil, 2 % glycerol and 1 % egg lecithin. These emulsions cannot be autoclaved. Coalescence of the droplets of the internal phase is a typical sign of instability. All-in-one total parenteral nutrition admixtures are a typical example for parenterally administered emulsion (compare Sect. 13.9). 

The most important excipients in parenteral nutrition solutions are emulsifying agents. Lecithin and phosphatides are mostly used. The emulsifying capacity of phosphatides correlates with their ionisation rate and thereby the pH of the emulsion. The pH also influences the stability of the hpid droplets [58]. If the pH decreases below 3, the droplet surfaces are no longer negatively charged and the droplets coalesce (see Sect. 18.4.1). If necessary, the pH is adjusted with an aqueous solution of sodium hydroxide or hydrochloric acid. 

Commercial fat emulsions employed in parenteral nutrition are stabilised by egg lecithin, which is a complex mixture of phospholipids with the following composition phosphatidylcholine (PC) 7.3%, lysophosphatidylcholine (LPC) 5.8%, phosphatidylethanolamine 15.0%, lysophosphatidylethanolamine (LPE) 2.1%, phos-phatidylinositol (PI) 0.6%, and sphingomyelin (SP) 2.5%. 

Amino acid-glucose solutions used in total parenteral nutrition of humans lack choline. The lipid emulsions that deliver extra calories and essential fatty acids during parenteral nutrition contain choline in the form of lecithin (20% emulsion contains 13.2 mmol 1 ). Humans treated with parenteral nutrition require 1-1.7 mmol of choline-containing phospholipid per day during the first week of parenteral nutrition therapy to maintain plasma choline levels. 

Buchman AL, Dubin M, Jenden D, Moukarzel A, Roch MH, Rice K, Gornbein J, Ament ME, and Eckhert CD (1992) Lecithin increases plasma free choline and decreases hepatic steatosis in long-term total parenteral nutrition patients. Gastroenterology 102 1363-1370. 

---