Synonyms:

Cysteine Hydrochloride

Generic Available:

Yes

Use:

Supplement to crystalline amino acid solutions, in particular the specialized pediatric formulas (eg, Aminosyn® PF, TrophAmine®) to meet the intravenous amino acid nutritional requirements of infants receiving parenteral nutrition (PN)

Contraindications:

Hypersensitivity to cysteine or any component of the formulation; patients with hepatic coma or metabolic disorders involving impaired nitrogen utilization

Warnings/Precautions:

Use with caution in patients with renal dysfunction and hepatic insufficiency. Metabolic acidosis has occurred in infants related to the "hydrochloride" component of cysteine; each 1 mmol cysteine (175 mg) delivers 1 mEq chloride and 1 mEq hydrogen ion; to balance the extra hydrochloride ions and prevent acidosis addition to the PN solution of a 1 mEq acetate electrolyte salt for each mmol (175 mg) of cysteine may be needed; each 40 mg cysteine (equal to every 1 g amino acid when used in the recommended ratio) adds 0.228 mEq chloride and hydrogen.

Adverse Reactions:

Frequency not defined.

Central nervous system: Fever

Endocrine & metabolic: Metabolic acidosis

Gastrointestinal: Nausea

Renal: Elevated BUN, azotemia

Stability:

Avoid excessive heat, do not freeze; when combined with parenteral amino acid solutions, cysteine is relatively unstable; it is intended to be added immediately prior to administration to the patient; infusion of the admixture should begin within 1 hour of mixing or refrigerated until use; stable 24 hours in PN solution; opened vials must be used within 4 hours of entry

Mechanism of Action:

Cysteine is a sulfur-containing amino acid synthesized from methionine via the transulfuration pathway. It is a precursor of the tripeptide glutathione and also of taurine. Newborn infants have a relative deficiency of the enzyme necessary to affect this conversion. Cysteine may be considered an essential amino acid in infants.

Dosage:

Neonates and Infants: I.V.: Added as a fixed ratio to crystalline amino acid solution: 40 mg cysteine per g of amino acids; dosage will vary with the daily amino acid dosage (eg, 0.5-2.5 g/kg/day amino acids would result in 20-100 mg/kg/day cysteine); individual doses of cysteine of 0.8-1 mmol/kg/day have also been added directly to the daily PN solution; the duration of treatment relates to the need for PN; patients on chronic PN therapy have received cysteine until 6 months of age and in some cases until 2 years of age

Administration:

Parenteral: Use only after dilution into PN solution; dilute with amino acid solution in a ratio of 40 mg cysteine to 1 g amino acid: eg, 500 mg cysteine is added to 12.5 g (250 mL) of 5% amino acid solution

Monitoring Parameters:

BUN, ammonia, electrolytes, pH, acid-base balance, serum creatinine, liver function tests, growth curve

Additional Information:

Addition of cysteine to PN solutions enhances the solubility of calcium and phosphate by lowering the overall pH of the solution.

Dental Health: Effects on Dental Treatment:

No significant effects or complications reported

Dental Health: Vasoconstrictor/Local Anesthetic Precautions:

No information available to require special precautions

Dosage Forms:

Injection, solution, as hydrochloride: 50 mg/mL (10 mL, 50 mL)