In order to examine the stability of vitamins in a T P N admixture stored in 3-litre plastic (EVA) bags, two different stability studies were performed. In the first experiment the TPN admixture was stored in darkness at 2-8°C for 96 h and the stability of vitamins determined. The vitamins examined were retinyl palmitate, a-tocopherol, thiamine mononitrate, sodium ascorbate (analysed as reduced ascorbic acid and dehydroascorbic acid), sodium riboflavin-5'-phosphate, pyridoxine hydrochloride, nicotinamide, folic acid, biotin, sodium pantothenate and cyanocobalamin.In the second test the stability of vitamins was determined during simulated infusion from the bag containing the admixture. The vitamins examined were retinyl palmitate, a-tocopherol, sodium riboflavin-5'phosphate and sodium ascorbace (analysed as reduced ascorbic acid and dehydroascorbic acid).The vitamin stability was found to be acceptable for all vitamins except ascorbic acid and folic acid. Total ascorbic acid is the sum of reduced ascorbic acid and dehydroascorbic acid (DHA). It is important to estimate the total ascorbic acid concentration because DHA is also biological active.About 50% of the nominal total ascorbic acid remained after 96 h of storage at 2 4°C in darkness, or after 24 h of simulated infusion initiated immediately after mixing.With folic acid there appears to be assay interference which requires further investigation. I N T R O D U C T I O NTotal parenteral nutrition (TPN) by means of premixed fat, glucose, amino acids, fat-and water-soluble vitamins, trace elements and electolytes in 3-litre plastic bags is now common, The physical and chemical stability of such systems has been extensively evaluated (1,2) and their clinical usefulness has been documented (3).

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The adsorption of diazepam to infusion sets and plastic syringes was studied. Infusion solutions consisting of diazepam injection (Valium) in glucose 5.5%, or diazepam emulsion in a lipid emulsion (Intralipid 10%) were infused through two different infusion sets (Transcodan L-74 and Cutter IL). It was found that, when an infusion solution with a low diazepam concentration (0.04 mg/ml) was infused slowly (4 ml/h), the diazepam adsorption was more than 80%. At a higher diazepam concentration (0.1 mg/ml) and increased infusion rate (20ml/h) the adsorption decreased. Diazepam injection in glucose 5.5% was adsorbed to a higher degree (40-75%) than diazepam emulsion in glucose 5.5% (15-35%). When diazepam emulsion was diluted with the lipid emulsion, no diazepam adsorption to the infusion set occurred at this concentration and infusion rate. No significant difference between the two infusion sets could be found. The miscibility of diazepam emulsion with glucose 5.5%, glucose 10%, or sodium chloride 0.9% was examined. Diazepam emulsion proved to be miscible with glucose 5.5% and glucose 10%, but sodium chloride should not be used to dilute diazepam emulsion. The effect on the diazepam concentration of storing diazepam injection and diazepam emulsion in plastic syringes for up to 4h was also studied. It was found that the diazepam concentration remained unchanged during this time.

Summary. Lipid particles of soya bean oil emulsions prepared with various emnlsifj'ing agents (egg yolk phosphatides, acetylated monoglycerides and polyoxypropylene-polyoxyethylene polymers) were examined in sections of osmiumfixed pellets. The mean particle size fell within the range of 0-3 to 0-8 fini for all but one emulsion and did not appear to be related to the emulsifying system used.Morphologically, particles of emulsions containing phosphatides were coated by an electron dense granular surface layer which was absent with the other emulsifiers. The presence of drugs in the oil phase did not alter the appearance of the lipid particles.