Cysteine Hydrochloride Injection, USP 0.5 gram is intended for use only after dilution in Aminosyn (a crystalline amino acid solution). Each 10 mL of Cysteine Hydrochloride Injection, USP 0.5 gram should be combined aseptically with 12.5 grams of amino acids, such as that present in 250 mL of Aminosyn 5%. The admixture is then diluted with 250 mL of dextrose 50% or such lesser volume as indicated. Equal volumes of Aminosyn 5% and dextrose 50% produce a final solution which contains Aminosyn 2.5% in dextrose 25%, which is suitable for administration by central venous infusion. Administration of the final admixture should begin within one hour of mixing due to the oxidative degradation of cysteine in the higher pH environment of the amino acid and dextrose admixture. Otherwise, the admixture should be refrigerated immediately and used within 12 hours of the time of mixing.

N-acetyl-L-cysteine (NAC) (1 µM ~ 1 mM) and cysteine (10 µM ~ 1 mM) increased [Ca(2+)]i in human neutrophils in a concentration-dependent manner. In Ca(2+)-free buffer, NAC- and cysteine-induced [Ca(2+)]i increase in human neutrophils completely disappeared, suggesting that NAC- and cysteine-mediated increase in [Ca(2+)]i in human neutrophils occur through Ca(2+) influx. NAC- and cysteine-induced [Ca(2+)]i increase was effectively inhibited by calcium channel inhibitors SKF96365 (10 µM) and ruthenium red (20 µM). In Na(+)-free HEPES, both NAC and cysteine induced a marked increase in [Ca(2+)]i in human neutrophils, arguing against the possibility that Na(+)-dependent intracellular uptake of NAC and cysteine is necessary for their [Ca(2+)]i increasing activity. The results show that NAC and cysteine induce [Ca(2+)]i increase through Ca(2+) influx in human neutrophils via SKF96365- and ruthenium red-dependent way.