# N-acetylcysteine (NAC) supplements

Source: https://onco.cc/technologies/n-acetylcysteine-supplements/  
OnCo record `n-acetylcysteine-supplements` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

N-acetylcysteine is a real medicine for paracetamol overdose and for thinning mucus, and is also sold as an antioxidant supplement. In a large trial it did not prevent second cancers of the head and neck or lung, and in animals it sped up lung cancer growth. Whether it interferes with cancer treatment is unknown, so it is one to discuss with your team.

## Summary

Memorial Sloan Kettering's About Herbs entry separates the prescription uses of N-acetylcysteine, as the antidote to paracetamol (acetaminophen) poisoning and as a mucolytic, from its sale as a supplement for liver protection and immunity. For cancer prevention, small studies suggested effects on biomarkers, but a large trial found it did not inhibit the formation of second head and neck or lung tumours. Preliminary studies suggest NAC may reduce some treatment side effects such as liver toxicity, neuropathy, mucositis or poor blood counts, but it did not reduce cisplatin toxicities or oxidative stress, and MSK states it is unclear whether, as an antioxidant, it may alter how well cancer treatment works. In an animal model NAC appeared to accelerate lung cancer growth. MSK's special point for patients: because some cancer treatments kill cells by generating free radicals, high doses of antioxidants could protect cancer cells as well as healthy ones. Side effects are mainly gastrointestinal; NAC adds to the blood-pressure-lowering and headache effects of nitroglycerin.

## Fields

- Kind: Technology
- Status: negative
- Last checked: 2026-11-04
- Also known as: NAC; Acetylcysteine
- Tags: complementary; supportive-care; evidence:no-benefit
- Principle: A precursor of glutathione that replenishes the cell's main antioxidant; that is why it protects the liver after paracetamol overdose, and why it could also protect cancer cells under oxidative attack.
- Strengths: Proven antidote for paracetamol overdose; Small signals for some treatment side effects
- Limitations: A large trial found no prevention of second head and neck or lung cancers; Accelerated lung cancer growth in an animal model; Unknown effect on chemotherapy and radiotherapy efficacy

## Sources

- MSK About Herbs: N-acetylcysteine (page last updated 21 October 2022): https://www.mskcc.org/cancer-care/integrative-medicine/herbs/n-acetylcysteine

## Connected records

- technologies: [Alpha-lipoic acid](https://onco.cc/technologies/alpha-lipoic-acid/), [Dietary supplements during cancer treatment: interactions and harms](https://onco.cc/technologies/dietary-supplements-treatment-interactions/), [Evidence-based integrative oncology](https://onco.cc/technologies/integrative-oncology/), [SAM-e (S-adenosylmethionine)](https://onco.cc/technologies/sam-e-supplements/), [Vitamin E supplements](https://onco.cc/technologies/vitamin-e-supplements/)
- cancers: [Head and neck squamous cell carcinoma](https://onco.cc/cancers/head-and-neck/), [Lung cancer (all types)](https://onco.cc/cancers/lung-cancer/)
- fronts: [Diet, Exercise & Lifestyle](https://onco.cc/fronts/nutrition-lifestyle/), [Prevention & Risk](https://onco.cc/fronts/prevention/), [Supportive Care & Survivorship](https://onco.cc/fronts/supportive-care/)
- drugs: [Cisplatin](https://onco.cc/drugs/cisplatin/)
- bottlenecks: [Misinformation and unproven therapies](https://onco.cc/bottlenecks/b-misinformation/)

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