Storage of mixtures for total parenteral nutrition III. Stability of vitamins in TPN mixtures.
TPN mixtures should contain all nutritional element necessary in the nutritional therapy--including unstable vitamins. In this study the stability of ascorbic acid and folic acid was investigated in a TPN mixture containing 12 vitamins by HPLC and microbiological assays. The degradation of both vitamins proceeded by first order kinetics. Half-lives for ascorbic acid were 1.1 h, 2.9 h, and 8.9 h when stored at 24 degrees C by daylight, 24 degrees C protected from light, and 4 degrees C protected by light, respectively. Under similar conditions half-lives for folic acid were 2.7 h, 5.4 h, and 24 h. The degradation rates found make pre-addition of these two vitamins to TPN mixtures questionable, storage for longer periods is inappropriate. For TPN patients receiving additional fluid intravenously it was found that addition of multivitamins to isotonic NaCl-solution was advisable. For other TPN patients alternative ways of vitamin administration might be preferable. When testing the stability of vitamins in TPN mixtures it was found that the brand of multivitamin preparation used was of importance. It should be stressed that data on the stability of vitamins derived from studies on the addition of a single vitamin cannot be extrapolated to multivitamin preparations because of possible mutual vitamin interactions.