Chemical stability of selenious acid in total parenteral nutrition solutions containing ascorbic acid

Parenteral nutrition compatibility and stability: A comprehensive review

Several guidance documents support best practices across the stages of the parenteral nutrition (PN)-use process to optimize patient safety. The critical step of PN order verification and review by the pharmacist requires a contextual assessment of the compatibility and stability implications of the ordered PN prescription. This article will provide working definitions, describe PN component characteristics, and present a wide-ranging representation of compatibility and stability concerns that need to be considered prior to preparing a PN admixture. This paper has been approved by the ASPEN Board of Directors. This article is protected by copyright. All rights reserved.

Technical aspects of trace element supplementation

Routine supplementation of total parenteral nutrition mixtures with the readily available single or combination trace elements products is becoming more widespread. As more is learned about deficiency syndromes and monitoring techniques, so too must we understand more about the physicochemical interactions between individual trace elements and other nutrients, that could ultimately affect bioavailability. Expert pharmaceutical assessment of these complex reactions, that have been demonstrated to occur in solution, becomes increasingly important in order to optimize the efficacy of micronutrient therapy.

Compatibility and stability of additives in parenteral nutrition admixtures

The addition of additives (electrolytes, trace elements, and vitamins) to parenteral nutrition (PN) mixtures can lead to precipitation as a result of physical incompatibilities and can lead to chemical degradation of individual ingredients. The most significant cause of precipitation is excessive concentrations of calcium phosphate. The most significant cause of chemical instability is the oxidation of specific vitamins. The factors influencing calcium phosphate solubility include the commercial amino acid source, the calcium and phosphate salts used, temperature, magnesium concentration, and final volume. Precipitation can be avoided by organic phosphates. Trace element precipitation is most commonly caused by the formation of iron phosphate salts or copper cysteinate in cysteine-containing amino acid infusions. The least stable nutrient is ascorbic acid, which reacts with oxygen, and is catalyzed by copper ions. Oxygen originates from PN ingredients, the filling process, air remaining in the bag after filling, and oxygen permeation through the bag wall. Storage in multilayered bags with reduced gas permeability can protect residual ascorbic acid. Other chemical losses are caused by the reduction of thiamine by metabisulfite, and photodegradation of daylight-sensitive vitamins, especially retinol and riboflavin, during administration.

Influence of combined use of selenious acid and SH compounds in parenteral preparations

The influence of the combined use of selenious acid and SH compounds (glutathione (GSH) and cysteine (Cys), or ascorbic acid (Asc)) on cultured venous vascular cells was investigated experimentally. When cultured human umbilical venous vascular endothelial cells were exposed to 10 microM of selenious acid combined with 0.5 mM-GSH or 0.5 mM-Cys, the release rates of [3H]-adenine and lactate dehydrogenase (LDH) from cells into the medium increased significantly as compared with after exposure to selenious acid alone, and damage to the vascular endothelial cells was found to be intensified. Addition of 1 microM of selenious acid simultaneously with 0.5 mM-GSH or 0.5 mM-Cys showed no differences in toxicity for the vascular endothelial cells as compared with the addition of selenious acid alone. On the other hand, simultaneous exposure to 10 microM of selenious acid and 1 mM-Asc induced no significant differences in the release rates of [3H]-adenine and LDH, and no damage was observed to the vascular endothelial cells. These results suggest that simultaneous addition of selenious acid together with GSH or Cys, which have the SH-group, may cause damage to the vascular endothelial cells. Therefore careful attention is warranted in total parenteral nutrition (TPN).

Assessment of trace element compatibility in total parenteral nutrition infusions

The application of X-ray energy dispersive spectroscopy to detect elements collected from TPN mixtures on membrane filters has been investigated. Many simple total parenteral nutrition mixtures prepared aseptically in large bags can be stored for extended periods. Trace elements are normally excluded from such bags, because not enough is known about their long-term stability and compatibility in total parenteral nutrition mixtures. Assessing the compatibility of many trace elements by conventional methods that rely on detecting concentration changes is extremely difficult. Analysis of precipitates from total parenteral nutrition mixtures confirmed that the proposed method was capable of identifying a number of elements from the mixture in complex precipitates, including calcium, phosphorus, iron, copper and selenium.

Prefilter and postfilter cysteine/cystine and copper concentrations in pediatric parenteral nutrition solutions

Pediatric amino acid products contain lower concentrations of methionine and require the addition of L-cysteine HCl just before infusion. Reports of a potential interaction between cysteine and copper, a routine addition to parenteral nutrition solutions, have appeared in the literature. This study serially evaluated cysteine/cystine and copper concentrations pre- and postfilter (0.22 microns) in two parenteral nutrition formulations prescribed for normal fluid (NF) or fluid-restricted (FR) pediatric patients. Solutions were infused via a peristaltic pump in vitro for 24 hours. Pre- and postfilter samples were obtained immediately after the infusion began (time 0) and at 1, 2, 3, 4, 8, 12, 16, 20, and 24 hours during the infusion. At 24 hours pre- and postfilter, cysteine/cystine were quantitated at 87.3% and 85% of the initial concentrations, respectively, for the NF solution and 92% and 91.5% for the FR solution. Pre- and postfilter copper was quantitated at 87.5% and 92.5% of the initial concentrations, respectively, for the NF solution and 88.2% and 95.2% for the FR solution. The 24 hour area under the curve for cysteine/cystine was 88.4% for the NF solution and 96.4% for the FR solution. For copper, the area under the curve for the NF solution was 99% and 96.7% for the FR solution. There was no visual evidence of incompatibility or precipitation. We conclude that copper-containing parenteral nutrition solutions with L-cysteine HCl added immediately before infusion are relatively stable after compounding and infusion over 24 hours.