With nitroglycerin or organic nitrates
Safety flag
Systemic acetylcysteine can potentiate nitrate-related vasodilation, headache, and hypotension.
Interaction evidence source All research profiles
Antioxidant / mucolytic
Acetylcysteine
Prepared by the ezGLP team. Sources last checked . Profile reviewed .
Also known as N-acetylcysteine, NAC
Routes represented in the knowledgebase: Oral / Inhaled / Other / unspecified.
Educational overview
Prescription forms have specific toxicology and respiratory indications; general antioxidant and recovery uses are off-label or supplement uses.
Acetylcysteine (N-acetylcysteine, NAC) is the N-acetyl derivative of the amino acid L-cysteine. It is a small thiol compound with three pharmacologic roles: as a mucolytic it breaks disulfide bonds in mucus glycoproteins, lowering the viscosity of airway secretions; as an antidote it restores hepatic glutathione and detoxifies the reactive acetaminophen metabolite NAPQI; and as a supplement it is marketed as a glutathione precursor and antioxidant, since cysteine availability is the rate-limiting step in glutathione synthesis. Acetylcysteine also has modest effects on glutamate signaling through the cystine-glutamate antiporter, which underlies its investigation in psychiatry. It belongs to the class of sulfhydryl-containing amino acid derivatives rather than to vitamins or peptides.
Evidence is strong and long established for acetaminophen (paracetamol) overdose, where intravenous acetylcysteine has been the standard antidote since Prescott's 1979 report in the British Medical Journal and is reviewed in a 2008 New England Journal of Medicine article. Randomized trials support oral acetylcysteine for reducing exacerbations in chronic bronchitis and COPD, with modest effect sizes. A 2015 systematic review of clinical trials in psychiatry and neurology found encouraging but preliminary results in addiction, compulsive disorders, schizophrenia, and bipolar depression, mostly from small academic trials. Large trials have not supported acetylcysteine for preventing contrast-induced kidney injury. Claims about fertility, immunity, or general antioxidant benefit rest on small or mechanistic studies.
Acetylcysteine is an FDA-approved prescription drug in two families of products: an inhalation and oral solution first approved in 1963 as a mucolytic and oral antidote, and Acetadote, an intravenous formulation approved in 2004 for acetaminophen overdose. Its supplement status is contested. In 2020 FDA stated that NAC is excluded from the dietary supplement definition because it was approved as a drug before being sold as a supplement; after a citizen petition and litigation, FDA issued a 2022 guidance announcing enforcement discretion, allowing NAC supplements to remain on sale while rulemaking is considered. In much of Europe, oral acetylcysteine is a non-prescription cough and mucolytic medicine. Compounded intravenous NAC sold by wellness clinics is not an FDA-approved product.
Storage differs by product. Acetadote vials are kept at room temperature and, once opened, the label limits use to 24 hours. Inhalation and oral solution is stored at room temperature unopened but refrigerated after opening and discarded after 96 hours; a sulfur odor is normal. Supplement capsules are stored dry at room temperature. For a dose log or inventory record, relevant details include the product form and route, the concentration for solutions, lot number, and the source, because the safety profile of intravenous administration, which includes anaphylactoid reactions, differs sharply from oral use. Concurrent nitrate medicines are worth noting because systemic acetylcysteine can potentiate their blood-pressure-lowering effect.
- Category
- Antioxidant / mucolytic
- Routes represented
- Oral / Inhaled / Other / unspecified
- Storage context
- Follow the product or pharmacy label; requirements vary by route and formulation.
Published literature
No verified PubMed or DOI link is available for this entry.
Safety evidence
Common or reported: rash, flushing, itching, nausea.
Serious or important: anaphylaxis, hypotension, wheezing or bronchospasm, fluid overload with IV use.
IV risks should not be generalized to ordinary oral supplement use.
Safety evidence sourceInteraction evidence
These are general, pairwise evidence notes. Green identifies the potential-synergy category, while Lv3/Lv2/Lv1 communicates evidence strength; it does not guarantee benefit or cancel a safety warning.
With glutathione
Complementary evidenceLv3
A small clinical study in early septic shock reported lower lipid-peroxidation markers and improved clinical scores when acetylcysteine was added to glutathione.
Interaction evidence sourceRelated clinical studyFDA sterile-glutathione warningCommon questions
Is NAC a drug or a dietary supplement?
Both, with unsettled legal status in the United States. Acetylcysteine has been an FDA-approved prescription drug since 1963 for mucolytic use and acetaminophen overdose. In 2020 FDA stated that this prior drug approval excludes NAC from the legal definition of a dietary supplement, but in 2022 it issued a guidance exercising enforcement discretion, so NAC supplements remain on sale pending possible rulemaking. In many European countries, oral acetylcysteine is an over-the-counter medicine rather than a supplement.
What is NAC used for in medicine?
Its principal approved uses are as an antidote to acetaminophen (paracetamol) poisoning, given intravenously or orally within a defined window to prevent liver injury, and as a mucolytic to thin airway secretions in conditions such as chronic bronchitis, cystic fibrosis, and COPD. It has also been studied for preventing COPD exacerbations, for psychiatric conditions including addiction and obsessive-compulsive symptoms, and for polycystic ovary syndrome, with evidence that ranges from moderate to preliminary.
Does NAC raise glutathione levels?
Acetylcysteine supplies cysteine, the rate-limiting amino acid for glutathione synthesis, and in glutathione-depleted states such as acetaminophen overdose it clearly restores hepatic glutathione. In healthy people with normal glutathione stores, studies show smaller and less consistent changes in blood or tissue glutathione, because synthesis is regulated by feedback. Whether raising glutathione in healthy adults produces any health benefit has not been demonstrated in outcome trials.
What are the side effects of acetylcysteine?
Oral acetylcysteine most often causes nausea, vomiting, diarrhea, and an unpleasant sulfur taste or odor. Intravenous administration carries a risk of anaphylactoid reactions including flushing, rash, bronchospasm, and hypotension, which the Acetadote label describes and which are more frequent at the start of infusion. Fluid overload has been reported with intravenous use in small children. The interaction with nitrates, which can amplify headache and low blood pressure, is documented in human studies.
Further reading
- DailyMed, Acetylcysteine solution for inhalation and oral use
- DailyMed, Acetadote (acetylcysteine) injection
- FDA guidance for industry, Policy Regarding N-acetyl-L-cysteine (2022)
- FDA constituent update, enforcement discretion for certain NAC products
- Prescott et al., intravenous N-acetylcysteine for paracetamol poisoning, BMJ 1979
- Heard, acetylcysteine for acetaminophen poisoning, N Engl J Med 2008
- Deepmala et al., clinical trials of N-acetylcysteine in psychiatry and neurology, Neurosci Biobehav Rev 2015
- Iversen et al., N-acetylcysteine enhances nitroglycerin-induced headache, human study
Summarised from published literature for reference only, with citations to the source. Evidence is graded as reported and is not a recommendation to combine, dose, or use any compound.
For personal tracking and education only. Not medical advice, diagnosis, or treatment, and not a medical device. Peptides may be prescription-only or unapproved where you live. Consult a licensed healthcare professional.