N-Acetyl Cysteine

Acetylcysteine · NAC · N-Acetylcysteine

Snapshot

Indications	Contraindications
Acetaminophen overdose^{1, 2} COPD exacerbations³ Obsessive-compulsive related disorders⁴ Skin picking and trichotillomania^{5, 6} Substance craving⁷ Schizophrenia negative symptoms⁸

N-acetylcysteine (NAC) is a modified form of the amino acid cysteine that raises glutathione availability and loosens mucus by breaking disulfide bonds⁹. Supplementation follows from that antioxidant and glutamate-modulating effect. It is used for acetaminophen overdose, chronic bronchitis and chronic obstructive pulmonary disease (COPD), and as an adjunct in obsessive-compulsive and related disorders including skin picking and trichotillomania. It is also used in substance use disorders and for liver and kidney protection.

Evidence is strongest for acetaminophen overdose, where acetylcysteine reduces hepatotoxicity and mortality when started early¹. In COPD, a Cochrane review found mucolytics modestly reduce exacerbations³. In obsessive-compulsive disorder, glutamatergic add-ons to serotonin reuptake inhibitors outperformed placebo in a meta-analysis, while guidelines weakly recommend NAC for obsessive-compulsive related disorders. Results are mixed in schizophrenia and unsupported as monotherapy for depression⁴. In 2026, a randomized trial in young people with alcohol use disorder found no overall benefit, though those with moderate to severe disorder drank less¹⁰. Products list NAC as capsules and tablets; see Form comparison.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

79 sources, 65 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources