Adult: As part of parenteral nutrition regimen for patients with severe liver disease who may have impaired enzymatic processes and require TPN. Doses are based on the recommended daily protein (amino acid) requirement. As cysteine hydrochloride: 7 mg/g of amino acids (equivalent to 5 mg cysteine/g of amino acids) daily. Correct severe fluid, electrolyte, and acid-base disorders before administration. Child: As additive to crystalline amino acid solution to meet the intravenous nutritional requirements of those receiving TPN: As cysteine hydrochloride: Infants and children ≤11 years 30-40 mg/g of amino acids daily; a lower dose of 20 mg/g of amino acids daily may also be given; ≥12 years Same as adult dose. Dosage recommendations may vary among individual products. Refer to specific product guidelines. Correct severe fluid, electrolyte, and acid-base disorders before administration.
Contraindications
Inborn errors of amino acid metabolism, pulmonary oedema or acidosis due to low cardiac output; hepatic coma or metabolic disorders involving impaired nitrogen utilisation.
Special Precautions
Patients with cardiac insufficiency, diabetes (including prediabetic patients), pulmonary disease. Renal and hepatic impairment. Children (especially, infants). Pregnancy and lactation.
Monitor fluid and electrolyte status, blood glucose, kidney and liver functions, CBC and coagulation parameters; blood ammonia levels (if hepatic impairment is present), triglycerides (if adding lipid emulsion), acid-base balance, serum proteins, blood culture, urine osmolarity and glucose, nitrogen intake.
Lab Interference
May interfere with estimations of nitrogen-containing substances. May cause a false-positive result with the nitroprusside test for ketone bodies.
Action
Description: Mechanism of Action: Cysteine is a non-essential amino acid. Endogenously, it is synthesised from methionine by cystathionase via the tran-sulfuration pathway and serves as a precursor substrate for glutathione and taurine. As an exogenous source it provides cysteine to the systemic circulation of patients who cannot synthesise adequate quantities due to deficient or insufficient cystathionase activity.
Synonym: l-cysteine.
Chemical Structure
Cysteine Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 5862, L-Cysteine. https://pubchem.ncbi.nlm.nih.gov/compound/L-Cysteine. Accessed Feb. 26, 2021.
Storage
Store between 15-30°C. Protect from light and excessive heat.
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