Use of Cysteine Hydrochloride Injection To Increase the Solubility of Calcium and Phosphates in FreAmine III-Containing Paranteral Nutrition Solutions.

Numerous factors (including solution pH) that influence the amount of calcium and phosphates remaining in solution or precipitating from parenteral nutrition solutions have been identified. Increased solubility of calcium and phosphates can be achieved in parenteral nutrition formulations by using a suitable acidic additive to lower the pH from the natural unadjusted level. The purpose of this study was to evaluate the use of cysteine hydrochloride injection as an additive to FreAmine III-based parenteral nutrition solutions to increase the solubility of calcium and phosphates. In this study, five representative core parenteral nutrition formulations containing FreAmine III 1% to 5% were evaluated. Those formulations contained cysteine hydrochloride injection 0.5mL (25 mg) per gram of amino acids from FreAmine III to lower the pH. Varying amounts of calcium and phosphates were added to samples of the core formulations to identify the points at which precipitation just began to occur. Five series of concentrations with maxima of calcium 40 mEq/L and phosphates 40 mM/L were tested. The samples were evaluated by visual observation with the unaided eye and with a Tyndall beam to accentuate the visibility of small particles and low-level turbidity. The turbidity and particle content of samples not exhibiting visible particles or haze were measured electronically. Evaluations were performed initially and after 24 and 48 hours of storage at 23 deg C and 37 deg C. Samples were also stored for 30 days at 4 deg C, were warmed at room temperature, and were evaluated after warming and after additional storage of 24 and 48 hours at room temperature. The addition of cysteine hydrochloride injection 5 mL/L for each 1% of amino acids content reduced the pH of the core parenteral nutrition admixtures from 6.4 to 5.9. The solubility of calcium and phosphates was increased by approximately 30% by that reduction in pH. The compatibility-incompatibility concentration ranges for each of the five core formulations, in which calcium ranged up to 40 mEq/L and phosphates ranged up to 40 mmol/L at temperatures of 23 deg C and 37 deg C are presented in tables and figures. The addition of cysteine hydrochloride 0.5 mL (25 mg) per gram of amino acids from FreAmine III increased the solubility of calcium and phosphates about 30% by lowering the solution pH.