Cysteine: uses, dosing, side effects & brands
Cysteine is a medicine sold in the U.S. under 2 brand and generic names. Below: what the FDA label says, every product that contains it, what the pills look like, and its recall record.
Key facts
- Available as
- Injectable
- Sold as
- 2 products — Elcys and Nouress
- Prescription?
- Prescription only
- Generic available?
- Not in our catalog
How cysteine is dosed
From the FDA label for Elcys (application NDA210660). Other cysteine products — different forms, different strengths — are dosed differently. Follow the label for the one you were prescribed.
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…
Cysteine side effects
The 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.
Who shouldn’t take cysteine
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. • Patients with pulmonary edema or acidosis due to low cardiac output. • Hypersensitivity to one or more amino acids ( 4 ) • Inborn errors of amino acid metabolism ( 4 ) • Pulmonary edema or acidosis due to low cardiac output ( 4 )
Every cysteine product we track (2)
Same active ingredient — different manufacturer, form, price and FDA recall record. That last one is what our independent score measures.
| # | Drug | Rating | Type | Form | Generic? | Pharmacy pays | |
|---|---|---|---|---|---|---|---|
| 1 | Not yet rated | Prescription | Injectable | No data | — | View → | |
| 2 | Not yet rated | Prescription | Injectable | No data | — | View → |
Cysteine recalls
From the FDA Enforcement database. A recall covers specific lots — not the drug as a whole.
How long cysteine keeps
The date on a sealed pack is not the only one: some cysteine labels start a second clock once the product is opened or mixed, as short as 4 hours.
Does cysteine expire? The in-use limits and storage rules from its labelsWhat people report to the FDA about cysteine
The FDA Adverse Event Reporting System (FAERS) collects reports from patients and clinicians. It holds 197 reports naming cysteine, and the FDA flagged 95% of those reports as serious. The effects reported most often — leaving out reports about overdose, misuse or the condition being treated, which dominate the raw list for common medicines:
- pyrexia15 reports
- hepatic function abnormal13 reports
- pruritus12 reports
- nausea11 reports
- diarrhoea10 reports
- vomiting10 reports
- pneumonia9 reports
- alanine aminotransferase increased7 reports
Read these as a signal, not a rate. A report does not mean cysteine caused the effect — anyone can file one, and many describe people taking several medicines for several conditions. Crucially there is no denominator: FAERS does not record how many people took the drug, so these counts cannot be turned into “X% of patients” — a bigger number often just means a more widely used or more talked-about drug. Duplicates exist, and publicity drives reporting. For what is actually established, read the FDA label section above.
Source: openFDA drug/event (FAERS), retrieved August 25, 2026.
Related calculators
Frequently asked questions
What is cysteine?
Elcys (Cysteine Hydrochloride) is a medication supplied as an injection, solution.
Can you take cysteine with other medicines?
It depends on the medicine. We check it against the FDA labels rather than guessing: our interaction checker searches each drug's own label for the other and quotes what it says, naming the section it came from. Run cysteine against whatever else you take — and remember that a label not naming a drug is not the same as that combination being safe.
What brand names is cysteine sold under?
We track 2 cysteine-containing products in the U.S.: Elcys and Nouress. They are the same active ingredient; they differ in form, manufacturer, price and FDA recall record.
What forms does cysteine come in?
Across the brands we track, cysteine is currently marketed as injectable, per the FDA's National Drug Code Directory. Each form is dosed differently — follow the label for the exact product you were prescribed.
Is there a generic cysteine?
We do not currently list a generic-labelled cysteine product. That does not always mean none exists — it means none appears under a generic name in the FDA data we track. Ask your pharmacist.
Has cysteine been recalled?
The FDA's Enforcement database lists 1 recall record whose product description mentions cysteine. The most recent: N-Acetyl-L-Cysteine for Injection (Jul 30, 2025). A recall applies to specific lots, not to the drug as a whole — check the record for the affected lot numbers.
Cite this page
- APA
- pharmaranks. (2026, July 24). Cysteine: uses, dosing, side effects & brands. https://pharmaranks.com/drugs/cysteine
- MLA
- “Cysteine: uses, dosing, side effects & brands.” pharmaranks, 24 July 2026, https://pharmaranks.com/drugs/cysteine.
We summarise public FDA and NIH sources — for a clinical claim, cite the primary source we link to as well.
Sources: FDA openFDA drug label, National Drug Code Directory, and Enforcement (recall) database. This page reproduces public FDA data and is not medical advice. Dosing is set by your prescriber.
Read the full FDA label for cysteine on DailyMed (NIH) ↗.