Cysteine

Nutritional supplement: Additive to crystalline amino acid solutions to meet the intravenous (IV) amino acid nutritional requirements of infants receiving total parenteral nutrition (TPN)

Hepatic coma; metabolic disorders involving impaired nitrogen utilization

Nutritional supplement: IV: Infants (receiving PN): Added as a fixed ratio to crystalline amino acid solution: 40 mg cysteine per 1 g of amino acids; dosage will vary with the daily amino acid dosage; (eg, 1 to 3 g/kg/day of amino acids would result in 40 to 120 mg/kg/day of cysteine); ASPEN recommends a range of 30 to 40 mg of cysteine per g of amino acids and suggests a dose as low as 20 mg per g of amino acids may be adequate and should be used in times of cysteine shortage (ASPEN Pediatric Nutrition Support Core Curriculum [Corkins, 2015]; Plogsted 2015); current practice suggests supplementation should be continued through the first year of life; practice varies widely (ASPEN Pediatric Nutrition Support Core Curriculum [Corkins 2015]; ASPEN [Mirtallo 2004]).

Store at 15°C to 30°C (59°F to 86°F). 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 may be refrigerated and used within 24 hours.

May interfere with estimations of nitrogen containing substances; do not withdraw venous blood for blood chemistries through the peripheral infusion site.

Cysteine is generally considered to be a nonessential amino acid in adults because it can be synthesized from methionine (an essential amino acid). The RDA for methionine + cysteine is increased in pregnant women (IOM, 2005).