What is the recommended dose of N-Acetylcysteine?

Doses below are the ones actually tested in the trials cited above, not a general recommendation. - **COPD:** 600mg twice daily (1,200mg/day) was the positive dose in PANTHEON. 600mg/day once dail...

Does N-Acetylcysteine interact with any medications?

N-Acetylcysteine lists 3 reported drug interactions whose sources are not yet verified, including interactions with Nitroglycerin, Blood-thinning drugs (warfarin, etc.), BP-lowering drugs. Check with your doctor before combining with prescription medications.

Ingredient Research

Graded against 178,763 supplements and 757 reviewed supplement and medication pairs, sourced from PubMed, FDA CAERS, openFDA, NIH DSLD

N-Acetylcysteine

Amino AcidLast updated August 24, 2026

AVELOR SUMMARY

NAC is a derivative of the amino acid L-cysteine. Its antioxidant activity is conventionally attributed to its role as a precursor to glutathione, and its mucus-thinning activity to its ability to break the disulphide bonds that cross-link mucus glycoproteins (Aldini 2018, PMID: 29742938). That mechanistic picture is contested. A 2021 review argues the glutathione-precursor and radical-scavenging explanations cannot be generalised across settings, and proposes conversion to hydrogen sulfide and sulfane sulfur species as an alternative account (Pedre 2021, PMID: 34171332). The clinical evidence collected below is mixed rather than uniformly positive. It is strongest for COPD exacerbations at 1,200mg/day, where a 1-year trial in 1,006 patients was positive while a 3-year trial at 600mg/day in 523 patients was null. Evidence across the psychiatric conditions studied is limited and partly null. Key safety concerns: a documented severe hypotension interaction with nitroglycerin, and a theoretical effect on clotting that warrants caution around surgery.

EVIDENCE GRADES

COPD exacerbations, at 1,200mg/day

Moderate evidenceGrade B

COPD lung function (FEV1, FVC, inspiratory capacity)No effect demonstrated

No benefit foundGrade D

Trichotillomania hair-pulling symptoms

Limited evidenceGrade C

Obsessive-compulsive and related disorders

Limited evidenceGrade C

Bipolar depressionNo benefit demonstrated

No benefit foundGrade D

OPTIMAL DOSAGE

Doses below are the ones actually tested in the trials cited above, not a general recommendation.

COPD: 600mg twice daily (1,200mg/day) was the positive dose in PANTHEON. 600mg/day once daily was null over 3 years in BRONCUS.
Trichotillomania: 1,200 to 2,400mg/day over 12 weeks in the single RCT.
Highest dose in any cited trial: 2,400mg/day. Tolerability above that is not established by the evidence collected here.
Routes: Oral, IV (medical), inhaled (respiratory)
Take with: Food to reduce GI effects

Scan a supplement containing N-Acetylcysteine

DRUG INTERACTIONS

Nitroglycerin

Severe hypotension + headache

Avoid combination.

Blood-thinning drugs (warfarin, etc.)

Increased bleeding risk

Use caution. Discontinue before surgery.

BP-lowering drugs

Additive hypotension

Monitor BP.

SAFETY PROFILE

Tolerability in the cited trials

PANTHEON: adverse events in 29% on NAC versus 26% on placebo over 1 year at 1,200mg/day.
Grant 2009: no adverse events in the NAC group over 12 weeks.
Kishi 2022: NAC was not associated with more gastrointestinal or other adverse events than placebo.
Rogliani 2019: adverse events across mucolytic and antioxidant agents were mild in severity and generally well tolerated.

Side Effects

Reported: Nausea, vomiting, dyspepsia, heartburn, diarrhea, headache, joint pain, dizziness. Frequency is not established by the trials cited above, which found adverse event rates similar to placebo.
Inhaled: Cough, bronchospasm
IV: Itching, rash, tachycardia, low BP

Precautions

Pregnancy: Caution. None of the trials cited above enrolled pregnant participants, so safety in pregnancy is not established by this evidence base.
Breastfeeding: Caution. No reliable safety data.
Asthma: Higher risk of allergic-like (anaphylactoid) reactions. Avoid unless medically indicated.
Surgery: Discontinue before surgery. The effect on clotting is theoretical rather than demonstrated, but the bleeding risk warrants caution.
Bleeding disorders: Use with caution.

WADA Status

Conditionally Prohibited. IV infusion >100mL per 12-hour period without medical indication is prohibited.

WHO SHOULD BE CAREFUL

HOW AVELOR SCORES THIS

Present at 1,200mg:✅ Green flag. This is the dose with positive RCT and meta-analytic support for COPD exacerbations.

Present at 600mg/day or below:⚠️ Yellow flag. Null on both primary outcomes in the 3-year BRONCUS trial.

Combined with nitroglycerin:🔴 Red flag. Severe hypotension documented.

Pre-surgery without discontinuation guidance:⚠️ Yellow flag. Bleeding risk.

In someone with asthma:⚠️ Yellow flag. Anaphylactoid reaction risk.

RELATED RESEARCH

5-HTP5-HTP (5-hydroxytryptophan) is an amino acid naturally produced in the body from

Acetyl-L-CarnitineMeta-analysis of 21 double-blind RCTs found significant cognitive improvement in MCI and early Alzhe

L-ArginineVINTAGE MI trial

BCAAs / EAAs

Scan Your N-Acetylcysteine Supplement Browse all ingredients

Independently graded against 178,763 indexed supplements and 757 reviewed supplement and medication pairs, sourced from PubMed, FDA CAERS, openFDA, and NIH DSLD | Last updated: August 24, 2026

Not medical advice. Based on published clinical research and systematic reviews.

Safety