Cysteine
/api/v1/drug/cysteineMechanism of action
Sourced from openFDAEndogenous cysteine is synthesized from methionine by the enzyme, cystathionase, via the trans-sulfuration pathway, and serves as a precursor substrate for both glutathione and taurine. ELCYS ® provides cysteine to the systemic circulation of patients who require PN and cannot synthesize adequate quantities of cysteine due to insufficient or deficient cystathionase activity.
Indications
Sourced from openFDA- ELCYS ® is indicated for use as an additive to amino acid solutions to meet the nutritional requirements of newborn infants requiring total parenteral nutrition (TPN); and of adult and pediatric patients with severe liver disease who may have impaired enzymatic processes and require TPN. It can also be added to amino acid solutions to provide a more complete profile of amino acids for protein synthesis.
Contraindications
Sourced from openFDA- ELCYS ® is contraindicated in: • Patients with known hypersensitivity to one or more amino acids. • Patients with inborn errors of amino acid metabolism due to risk of severe metabolic or neurologic complications.contraindicated
Dosage & administration
Sourced from openFDA• ELCYS ® is for admixing use only. Not for direct intravenous infusion . ( 2.1 ) • PHARMACY BULK PACKAGE: Dispense single-doses to many patients in a pharmacy admixture program. Use within 4 hours of puncture. ( 2.1 ) • See full prescribing information for information on preparation, administration, instructions for use, dosing considerations, including the recommended dosage in pediatric patients and adults. ( 2.1 , 2.2 , 2.3 , 2.4 , 2.5 ) 2.1 Important Administration Information Prior to administration, ELCYS® must be diluted and used as an admixture in PN solutions. ELCYS® is not for direct intravenous infusion. The resulting solution is for intravenous infusion into a central or peripheral vein. The choice of a central or peripheral venous route should depend on the osmolarity of the final infusate. Solutions with osmolarity of 900 mOsm/L or greater must be infused through a central catheter [see Warnings and Precautions ( 5.2 )] . ELCYS ® is supplied as a pharmacy bulk package, and consists of one pharmacy bulk vial which must be diluted prior to intravenous administration [see Dosage andAdministration ( 2.3 )]. As a pharmacy bulk vial, ELCYS ® is intended for dispensing of single doses to many patients. Dispensing from a pharmacy bulk vial should be completed within 4 hours after the vial is penetrated. Do not administer ELCYS ® as a direct, undiluted intravenous injection. 2.2 Preparation and Administration Instructions Prior to administration, ELCYS® must be diluted and used as an admixture in PN solutions. ELCYS® is not for direct intravenous infusion.
Warnings & precautions
Sourced from openFDA• Pulmonary Embolism due to Pulmonary Vascular Precipitates: If signs of pulmonary distress occur, stop the infusion and initiate a medical evaluation. ( 5.1 ) • Vein Damage and Thrombosis: Solutions with osmolarity of 900 mOsm/L or more must be infused through a central catheter. ( 2.1 , 5.2 ) • Increased blood urea nitrogen (BUN): Monitor laboratory parameters and discontinue if exceeds normal postprandial limits and continues to increase. ( 5.3 ) • Acid-Base Imbalance: Monitor laboratory parameters and supplement with electrolytes as needed. ( 5.4 ) • Hepatobiliary Disorders: Monitor liver function parameters and ammonia levels. ( 5.5 ) • Hyperammonemia: Neurocognitive delay possible in infants; monitor blood ammonia levels. ( 5.6 , 8.4 ) • Aluminium Toxicity: Increased risk in patients with renal impairment, including preterm infants. ( 5.7 , 8.4 ) • Monitoring and Laboratory Tests: Monitor fluid and electrolytes, serum osmolarity, blood glucose, kidney and liver function, blood count and coagulation parameters throughout treatment. ( 5.8 ) 5.1 Pulmonary Embolism due to Pulmonary Vascular Precipitates Pulmonary vascular precipitates causing pulmonary vascular emboli and pulmonary distress have been reported in patients receiving PN. In some fatal cases, pulmonary embolism occurred as a result of calcium phosphate precipitates. Precipitation following passage through an in-line filter and suspected in vivo precipitate formation has also been reported. If signs of pulmonary distress occur, stop the PN infusion and initiate a medical evaluation.
Adverse reactions
Sourced from openFDAThe following serious adverse reactions are discussed in greater detail in other sections of the prescribing information: • Pulmonary embolism due to pulmonary vascular precipitates [see Warnings and Precautions ( 5.1 )] • Vein damage and thrombosis [see Warnings and Precautions ( 5.2 )] • Increased BUN [see Warnings and Precautions ( 5.3 )] • Acid-base imbalance [see Warnings and Precautions ( 5.4 )] • Hepatobiliary disorders [see Warnings and Precautions ( 5.5 )] • Hyperammonemia [see Warnings and Precautions ( 5.6 )] • Aluminum toxicity [see Warnings and Precautions ( 5.7 )] Adverse reactions with the use of cysteine hydrochloride injection were identified in clinical studies or postmarketing reports. Because some of these reactions were reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. • Local infusion site reactions, including a warm sensation, erythema, phlebitis and thrombosis at the infusion site • Generalized flushing, fever and nausea Most common adverse reactions are local reactions (warm sensation, erythema, phlebitis and thrombosis at the infusion site), generalized flushing, fever and nausea ( 6 ). To report SUSPECTED ADVERSE REACTIONS, contact Exela Pharma Sciences, LLC or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
Use in specific populations
Sourced from openFDA8.1 Pregnancy Risk Summary Appropriate administration of ELCYS ® is not expected to cause major birth defects, miscarriage or adverse maternal or fetal outcomes. Animal reproduction studies have not been conducted with cysteine hydrochloride. The estimated background risk for major birth defects and miscarriage for the indicated populations is unknown. All pregnancies have a background risk of birth defect, loss or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defect and miscarriage in the clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. 8.2 Lactation Risk Summary Data available on the effects of cysteine hydrochloride on infants, either directly or through breastmilk, do not suggest a significant risk of adverse events from exposure. Although there are no data on the presence of cysteine hydrochloride in human or animal milk or the effects on milk production, appropriate administration of ELCYS ® is not expected to cause harm to a breastfed infant. The development and health benefits of breastfeeding should be considered along with the mother’s clinical need for ELCYS ® and any potential adverse effects on the breastfed infant from ELCYS ® or from the underlying maternal condition.
Overdosage
Sourced from openFDAIn the event of over hydration or solute overload, re-evaluate the patient and institute appropriate corrective measures [see Warnings and Precautions ( 5.3 , 5.4 , 5.5 , 5.7 , 5.8 )] .
Approval history
Sourced from openFDA- Jul 20, 1984NDANDA019018B Braun
- Jun 19, 2003ANDAANDA075880Baxter Hlthcare
- Apr 16, 2019NDANDA210660Exela Pharma
- Dec 13, 2019NDANDA212535Baxter Hlthcare Corp
FAERS reports
- 1Parenteral Nutrition Associated Liver Disease5036%
- 2Condition Aggravated117.9%
- 3Cholestasis96.4%
- 4Liver Function Test Abnormal96.4%
- 5Hallucination75.0%
- 6Malaise64.3%
- 7Pyrexia64.3%
- 8Dizziness53.6%
- 9Fatigue53.6%
- 10Hypokalaemia53.6%
- 11Nausea53.6%
- 12Pneumonia53.6%
- 13Asthenia42.9%
- 14Bacterial Infection42.9%
- 15Blood Bilirubin Increased42.9%
Literature
Recent PubMed references pinned to Cysteine as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.
- The cysteine metabolic regulation through CSE-transsulfuration pathway is essential in iron-induced oxidative damage of heart.Redox report : communications in free radical research · 2026 · Zhang Y, Xin Y, Zhou J, et al.PMID 42246934DOI 10.1080/13510002.2026.2684348
- N-acetylcysteine modulates neutrophil-driven immune and metabolic pathways in steatotic liver ischemia-reperfusion injury.Frontiers in immunology · 2026 · Kang J, Patil D, Hackett R, et al.PMID 42238593DOI 10.3389/fimmu.2026.1821592
- Covalent drugs reimagined: from cysteine-targeted inhibitors to proteome-informed precision therapeutics.Bioorganic chemistry · 2026 · Al-Karmalawy AA, Sippl W, Al-Dakhil A, et al.PMID 42229348DOI 10.1016/j.bioorg.2026.110065
- Albumin as a dynamic extracellular redox regulator: from Cys34 oxidation biomarkers to polysulfide-mediated homeostatic mechanisms and clinical applications.Redox report : communications in free radical research · 2026 · Ishima Y, Watanabe H, Ikeda-Imafuku M, et al.PMID 42228365DOI 10.1080/13510002.2026.2682043
- Mechanistic Evidence for Gold(III)-Mediated Arylation of the Cys-Sec Motif of Thioredoxin Reductase 1.Journal of peptide science : an official publication of the European Peptide Society · 2026 · Kanavos I, Nakahata DH, Messori L, et al.PMID 42226573DOI 10.1002/psc.70108
- Morphological and Biochemical Insights Into the Renoprotective Effects of Combined N-Acetylcysteine and Glycine Treatment in Experimental Diabetic Nephropathy.Pharmacology research & perspectives · 2026 · Ejubović M, Belančić A, Lam YW, et al.PMID 42220095DOI 10.1002/prp2.70273
- A novel ICP-MS strategy identifies arsenite as an inhibitor of selenocysteine-tRNA(Sec) charging.The Journal of toxicological sciences · 2026 · Takashima H, Makino R, Taguchi H, et al.PMID 42219356DOI 10.2131/jts.51.331
- Urinary volatile organic compound metabolites and premature menopause: Population-based, network toxicology, and experimental evidence with a focus on HEMA.Ecotoxicology and environmental safety · 2026 · Yang Q, Huang J, Xu Z, et al.PMID 42214307DOI 10.1016/j.ecoenv.2026.120318
Clinical trials
The 10 most recently updated of 725 ClinicalTrials.gov registrations naming Cysteine as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.
- The Effect of NAC on Lung Function and CT Mucus ScoreTerminated · Phase 4 · Interventional · 4 enrolled · University of California, San FranciscoNCT03822637updated 2026-06-11
- Assessment of the Impact of N-acetylcysteine Supplementation on Physical PerformanceCompleted · Interventional · 77 enrolled · Poznan University of Life SciencesNCT05604586updated 2026-06-10
- Effect of Topical Bromelain Versus Topical Corticosteroids in the Management of Oral Lichen PlanusRecruiting · Phase 2 · Interventional · 42 enrolled · Cairo UniversityNCT06981767updated 2026-06-09
- To Evaluate the Efficacy and Safety of N-acetyl Cysteine Administration in Patients With Diabetic RetinopathyRecruiting · Phase 4 · Interventional · 76 enrolled · Ain Shams UniversityNCT07634991updated 2026-06-09
- Bromelain for Post-surgery Facial SwellingRecruiting · Interventional · 200 enrolled · Mohamed BazinaNCT07115212updated 2026-06-05
- Antioxidant Therapy With N-acetylcysteine for Children With Neurofibromatosis Type 1Completed · Phase 2 · Interventional · 25 enrolled · Children's Hospital Medical Center, CincinnatiNCT04481048updated 2026-06-05
- Safety And Tolerability Of Gamma Glutamylcysteine (GGC) Oral Supplementation In MCI PatientsRecruiting · Phase 1 · Interventional · 9 enrolled · Pravat MandalNCT07583251updated 2026-06-03
- Monitoring Patients With Repetitive Head Impact With Gamma-glutamylcysteine SupplementationRecruiting · Phase 1 · Interventional · 30 enrolled · Pravat MandalNCT07050173updated 2026-06-03
- PROlonged Corticosteroid Treatment or N-ACetylcysteine for Severe Alcoholic HepatitisRecruiting · Phase 3 · Interventional · 477 enrolled · University Hospital, LilleNCT06956482updated 2026-06-01
- Topiramate Augmenting Strategies for the Treatment of Alcohol Use DisorderCompleted · Early phase 1 · Interventional · 17 enrolled · Nassima Ait-Daoud TiouririneNCT03120468updated 2026-05-27
Frequently asked questions
- How does Cysteine work?
- Endogenous cysteine is synthesized from methionine by the enzyme, cystathionase, via the trans-sulfuration pathway, and serves as a precursor substrate for both glutathione and taurine. ELCYS ® provides cysteine to the systemic circulation of patients who require PN and cannot synthesize adequate quantities of cysteine due to insufficient or deficient cystathionase activity.
- What is Cysteine used for?
- According to FDA labeling, Cysteine carries indications including: ELCYS ® is indicated for use as an additive to amino acid solutions to meet the nutritional requirements of newborn infants requiring total parenteral nutrition (TPN); and of adult and pediatric patients with severe liver disease who may have impaired enzymatic processes and require TPN. It can also be added to amino acid solutions to provide a more complete profile of amino acids for protein synthesis.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.
- What are the brand names for Cysteine?
- Cysteine is marketed under brand names including Elcys, Freamine III 10, Hepatamine 8, Nouress, PremaSol, ProcalAmine 3, Trophamine 10 %, Trophamine 6 %.
- What are the contraindications for Cysteine?
- Cysteine labeling lists contraindications including: ELCYS ® is contraindicated in: • Patients with known hypersensitivity to one or more amino acids. • Patients with inborn errors of amino acid metabolism due to risk of severe metabolic or neurologic complications.. Always consult the full prescribing information and a clinician.
cysteine is illustrative MVP content compiled from public sources. pharmacopeia is for educational and informational use only and is not a substitute for professional medical advice.