Probability-based compatibility curves for calcium and phosphates in parenteral nutrition formulations

Calcium and Phosphate Solubility Curve Equation for Determining Precipitation Limits in Compounding Parenteral Nutrition

Clinicians have published research and reports on calcium and phosphate solubility within parenteral nutrition (PN) for over 40 years. Foundational empirical laboratory investigation in the 1980s motivated by the prevalence of neonatal rickets and osteomalacia in the Neonatal Intensive Care Unit (NICU) population led to precipitation curves that have guided PN prescribing and compounding. Over subsequent decades, numerous publications have expanded the knowledge of factors influencing calcium and phosphate solubility in formulating optimal and safe PN admixtures. Failure to adhere to known principles has led to serious injury and death. Known solubility curves are derived from empiric analysis of a finite number of conditions and concentrations, whereas custom PN orders vary widely and rarely match the admixture composition in the data set used to derive the published precipitation curves. Various commercial platforms have been developed to aid the pharmacist in assessing the potential for precipitation when evaluating a PN order. Some applications plot the calcium and phosphate concentrations of the prescribed PN against known published graphs most similar to the order, allowing the pharmacist to judge the risk of precipitation. Other approaches use intellectually protected trade secret algorithms to determine calcium and phosphate solubility across a continuum of conditions. This publication reports equations that have been used successfully for over 2 decades in our regional network of NICUs and shared with others to determine safe prescribing limits for calcium and phosphate concentrations using an electronic PN prescribing program.

Use of sodium glycerophosphate in neonatal parenteral nutrition solutions to increase calcium and phosphate compatibility for preterm infants

BACKGROUND

Preterm infants require higher calcium and phosphate intake than term infants to facilitate adequate bone growth, but this is rarely met in parenteral nutrition (PN) solution because of the limited solubility of calcium and phosphate. This study aimed to evaluate the solubility of organic phosphate with calcium gluconate in neonatal PN solutions, simulating its clinical use.

METHODS

PN solutions were composed of calcium gluconate at 50 mEq/L and sodium glycerophosphate (NaGP) at 25 mmol/L. Another component included 1% or 4% amino acid and 10% or 20% dextrose. For comparison, PN solution composed of potassium phosphate was also evaluated. Each solution was evaluated using the following methods: visual inspection, light obscuration particle count test, and pH measurement. To simulate the clinical condition, the solution was tested after compounding, after being stored at 25 °C for 24 h, and after being stored at 2°C-8°C for 2 or 9 days and subsequently at 25 °C for 24 h.

RESULTS

There was no visual deposition in PN solution using NaGP in any of the concentrations and under any stored condition. The solution fulfilled the criteria of physical compatibility as < 25 particles/mL measuring ≥10 μm in diameter and <3 particles/mL measuring ≥25 μm in diameter. On the contrary, visual deposition was evidently noted in PN solution using potassium phosphate after its formulation, and the particle count significantly exceeded the range of physical compatibility.

CONCLUSION

NaGP and calcium gluconate have significantly good compatibility in PN solution. The use of NaGP in neonatal PN prevents calcium and phosphorus precipitation, hence increasing their supply to preterm infants in meeting their growth requirement.

Calcium/Phosphate Solubility Curves for Premasol and Trophamine Pediatric Parenteral Nutrition Formulations

OBJECTIVES

Calcium and phosphate incompatibility in parenteral nutrition formulations remains a critical concern for patient safety. This study examined calcium phosphate solubility for 2-in-1 admixtures prepared using 2 commercially available pediatric amino acid solutions (Premasol, Baxter Healthcare Corp; or Trophamine, B. Braun Medical Inc), applying identical test methods, storage conditions, and acceptance criteria.

METHODS

Parenteral 2-in-1 admixtures included amino acid; dextrose; static concentrations of sodium, potassium, and magnesium, and varying concentrations of calcium (0-60 mEq/L), phosphate (15-50 mmol/L), and cysteine. Three replicate samples were stored for 48 hours at 40°C ± 2°C and then visually inspected for particulate matter, evaluated for subvisible particulate matter, when particulate matter was noted, microscopic examination was performed to confirm the presence of calcium phosphate crystals. Pass criteria were: all replicates free of visible particulate matter related to calcium phosphate crystals and particle counts below US Pharmacopeia <788> limits.

RESULTS

Premasol and Trophamine generated identical calcium phosphate curves for 2% amino acid formulations containing 20% dextrose with/without cysteine, and similar curves for the 1% or 3% amino acid formulations containing 10% or 20% dextrose with/without cysteine. Calcium phosphate particles were identified in failed samples by scanning electron microscopy/energy dispersive X-ray spectroscopy. Calcium phosphate solubility was higher in formulations containing cysteine 40 mg/g amino acid vs. cysteine 20 mg/g amino acid and in cysteine 20 mg/g amino acid vs. no cysteine.

CONCLUSIONS

Admixtures made with 1%, 2%, or 3% Premasol or Trophamine have essentially equivalent calcium phosphate solubility curves when tested with identical methods, storage conditions, and acceptance criteria.

Calcium Chloride in Neonatal Parenteral Nutrition Solutions with and without Added Cysteine: Compatibility Studies Using Laser and Micro-Flow Imaging Methodology

BACKGROUND

Previous studies of compatibility of calcium chloride (CaCl2) and phosphates have not included particle counts in the range specified by the United States Pharmacopeia. Micro-flow imaging techniques have been shown to be comparable to light obscuration when determining particle count and size in pharmaceutical solutions.

OBJECTIVE

The purpose of this study was to do compatibility testing for parenteral nutrition (PN) solutions containing CaCl2 using dynamic light scattering and micro-flow imaging techniques.

METHODS

Solutions containing TrophAmine (Braun Medical Inc, Irvine, CA), CaCl2, and sodium phosphate (NaPhos) were compounded with and without cysteine. All solutions contained standard additives to neonatal PN solutions including dextrose, trace metals, and electrolytes. Control solutions contained no calcium or phosphate. Solutions were analyzed for particle size and particle count. Means of Z-average particle size and particle counts of controls were determined. Study solutions were compared to controls and United States Pharmacopeia (USP) Chapter 788 guidelines. The maximum amount of Phos that was compatible in solutions that contained at least 10 mmol/L of Ca in 2.5% amino acids (AA) was determined. Compatibility of these solutions was verified by performing analyses of 5 repeats of these solutions. Microscopic analyses of the repeats were also performed.

RESULTS

Amounts of CaCl2 and NaPhos that were compatible in solutions containing 1.5%, 2%, 2.5%, and 3% AA were determined. The maximum amount of NaPhos that could be added to TrophAmine solutions of > = 2.5% AA containing at least 10 mmol/L of CaCl2 was 7.5 mmol/L. Adding 50 mg/dL of cysteine increased the amount of NaPhos that could be added to solutions containing 10 mmol/L of CaCl2 to 10 mmol/L.

CONCLUSION

Calcium chloride can be added to neonatal PN solutions containing NaPhos in concentrations that can potentially provide an intravenous intake of adequate amounts of calcium and phosphorus.

Automated system for kinetic analysis of particle size distributions for pharmaceutically relevant systems

Detailing the kinetics of particle formation for pharmaceutically relevant solutions is challenging, especially when considering the combination of formulations, containers, and timescales of clinical importance. This paper describes a method for using commercial software Automate with a stream-selector valve capable of sampling container solutions from within an environmental chamber. The tool was built to monitor changes in particle size distributions via instrumental particle counters but can be adapted to other solution-based sensors. The tool and methodology were demonstrated to be highly effective for measuring dynamic changes in emulsion globule distributions as a function of storage and mixing conditions important for parenteral nutrition. Higher levels of agitation induced the fastest growth of large globules (≥5 μm) while the gentler conditions actually showed a decrease in the number of these large globules. The same methodology recorded calcium phosphate precipitation kinetics as a function of [Ca(2+)] and pH. This automated system is readily adaptable to a wide range of pharmaceutically relevant systems where the particle size is expected to vary with time. This instrumentation can dramatically reduce the time and resources needed to probe complex formulation issues while providing new insights for monitoring the kinetics as a function of key variables.