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.
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.
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.
Medication review
This source review is incomplete. It does not establish which combinations are safe or appropriate for you.
Nitroglycerin
Source review required
The likelihood of harm with other doses, formulations and populations remains unassessed. The oral study does not establish a routine oral-supplement hypotension rate or a blanket instruction to avoid the combination.
Severe headaches were reported more often with oral NAC plus nitroglycerin patches than with patches alone in one trial in adults with unstable angina. A separate hospital study reported symptomatic low blood pressure with intravenous NAC plus intravenous nitroglycerin. These findings do not establish the risk from routine oral supplements.
Discuss adding NAC with the clinician who prescribes your nitroglycerin.
Discussion with the nitroglycerin prescriber; no dose, timing or self-adjustment instruction.
Original PubMed abstract/metadata inspected in the prior pinned packet; complete report not claimed unless explicitly stated.
Activated charcoal
Source review required
A spacing interval for routine oral NAC supplements has not been established. The reviewed absorption studies do not demonstrate clinical treatment failure.
Activated charcoal may reduce absorption of oral acetylcysteine used in poisoning care. Small volunteer studies reported differing effects on absorption. This review does not establish a spacing rule for routine oral NAC supplements.
If acetylcysteine is being used in poisoning care, follow the treating team's instructions for acetylcysteine and activated charcoal.
Prescription oral acetylcysteine in poisoning care; not a supplement-spacing instruction.
Original PubMed abstract/metadata inspected in the prior pinned packet; complete report not claimed unless explicitly stated.
Anticoagulants
Source review required
The reviewed evidence does not establish the interaction risk for oral NAC with anticoagulants. It does not establish low clinical significance or a surgery stopping interval.
This review does not establish how oral NAC affects bleeding risk when combined with anticoagulants. Intravenous and laboratory findings do not quantify the risk from routine oral supplements.
This review has not established the interaction risk of routine oral NAC supplements with anticoagulants. Intravenous and laboratory findings do not establish a stopping interval before a procedure.