The Vitruvian Man, Leonardo da Vinci, 1490
The benefits are broad but the trials are limited
STUDY: Joy T et al, Clin Ter 2026
STUDY TYPE: Narrative review
FUNDING: Independent
Background
NAC has been around since the 1960s, first as a mucolytic, then as the antidote for acetaminophen overdose. It works mainly by replenishing glutathione, the body’s primary intracellular antioxidant, and by directly scavenging free radicals. This review looks at its potential across four organ systems: nervous, cardiovascular, respiratory, and renal.
Psychiatric disorders
The authors did not address this, so I’ll add a review. The most promising evidence is in schizophrenia, wher NAC Improved negative symptoms, memory, and processing speed, but not positive symptoms. Benefits may take 4-6 months to see; dose around 2,000 mg/day (1 large RCT, 8 small RCTs, 67% positive).
In other disorders, the trials are few and small, with mixed results in: bipolar depression, OCD, trichotillomania, and addictions (cannabis, opioid, nicotine, gambling). However, if the patient also has a medical problem that it treats below, it may be worth trying, including for prevention of renal disease on lithium.
Kidney disease
The evidence is strongest for contrast-induced nephropathy, where NAC consistently reduces acute kidney injury markers (dose around 2,000 mg daily). Benefits in chronic kidney disease and dialysis patients are promising but need more study. In animal models, it reduced renal toxicity from lithium.
Lung disease
COPD: NAC reduces exacerbations at 600–1,200 mg/day, and lowers sputum viscosity and inflammatory markers.
Idiopathic pulmonary fibrosis, results are mixed: the PANTHER-IPF trial found no benefit from monotherapy, though a genetic subgroup (TOLLIP rs3750920 TT genotype) may respond, and a new trial is testing this hypothesis.
Heart disease
Coronary Artery Disease: NAC improves endothelial function, lowers homocysteine levels, and may reduce post-operative atrial fibrillation, which complicates 20–50% of cardiac surgeries. Large, randomized trials, though, have shown inconsistent effects on mortality and arrhythmia.
Neurodegenerative disease
Preclinical data for Alzheimer’s and Parkinson’s are encouraging. NAC reduced cognitive decline and tau pathology in rat models, and small human Parkinson’s studies showed improved dopaminergic activity. Clinical trials in humans, however, have largely disappointed.
Problems
Oral bioavailability is low — roughly 4–10% — which likely explains why preclinical results often outperform clinical ones. Adverse effects are mostly mild gastrointestinal symptoms. Intravenous NAC carries a small risk of anaphylactoid reactions.
Practice Implications
- We generally don’t recommend treatments based on small, mixed trials. But what if the risk is low, alternatives are few, and the patient has several conditions that potentially benefit from the therapy? That’s the question NAC brings up.
- If you do use it, stick with lab-tested products like the ones here.
—Chris Aiken, MD
Director, Psych Partners
Editor in Chief, Carlat Psychiatry Report
