NAC: Medical Use in Acetaminophen Overdose, FDA Status as a Supplement and Safety

If acetaminophen (paracetamol) has been swallowed in excess

Get help immediately. In the US, call 911 or Poison Help at 1-800-222-1222, a free service open 24 hours a day, 7 days a week. [1] MedlinePlus states there is no home treatment and to seek medical help right away. [1] Symptoms may not appear until 12 or more hours after the medicine was swallowed, so feeling well at first does not rule out harm. [1] With treatment within 8 hours of the overdose the chance of recovery is very good. [1] Do not try to treat an overdose with a NAC supplement. Outside the US, see Poison Help by Country and Poisoning: What to Do First.

The short answer

N-acetylcysteine (NAC) is a hospital antidote for acetaminophen overdose. It is also sold as a supplement. In the US the FDA has said NAC is legally excluded from the definition of a dietary supplement, yet it has chosen not to take action against certain NAC products. That is not a ban, and it is not an endorsement. This page describes US regulation only.

NAC as a medicine

Emergency rooms may give an antidote, n-acetylcysteine, to counteract the effects of acetaminophen. [1] A different form is breathed in through a nebulizer as a mucolytic, a medicine that thins mucus in conditions such as asthma, emphysema, bronchitis and cystic fibrosis. [2] MedlinePlus also notes acetylcysteine is sometimes used for acetaminophen overdose and advises talking with the doctor about the risks. [2] These are clinician-directed medicines. A capsule or powder from a shop is not the same as a hospital treatment.

What the FDA said, step by step

What this does and does not mean

• Not a ban. The pages we read describe enforcement discretion for certain products, not a prohibition. [5]
• Not a permanent rule. The FDA wrote that it was considering rulemaking on whether NAC is excluded from the supplement definition. [4] It also said it would notify stakeholders by withdrawing or revising the guidance if it decided the policy was no longer appropriate. [4] The pages we read were current as of 2023; newer FDA actions are not described in the sources we read, so check FDA.gov.
• Not law. The guidance document says it does not have the force and effect of law. [5]
• Other countries. Rules in the UK, EU and Canada are not described in the sources we read. See Supplement Regulation by Country.
• Claims. Whether a supplement may be marketed does not tell you whether it works for any condition. For the research, see NAC Evidence.

Safety and who should ask first

Safety information for oral supplements comes mostly from trials and reports, not from a national limit; none is quoted here. Findings we read:

• A meta-analysis of 13 studies (4,155 people with chronic bronchitis or COPD) described NAC as well tolerated. [6]
• In a 16-week trial in adults with treatment-resistant obsessive-compulsive disorder, abdominal pain was reported more often with NAC than placebo. [7]
• A case report describes a 6-year-old who developed raised pressure inside the skull while taking oral NAC, which improved within 24 hours of stopping it. [8] This is one case, so it shows a possible link, not a proven one. Children should only use NAC under a clinician's direction.
• For the inhaled medicine, MedlinePlus lists nausea, vomiting and throat irritation, and says chest tightness, wheezing, difficulty breathing or swallowing, hives, rash or itching need urgent attention. [2] It tells people with asthma to inform their doctor. [2]
• Pregnancy and breastfeeding: MedlinePlus advises telling your doctor if pregnant, planning pregnancy or breastfeeding when acetylcysteine is prescribed. [2] Ask a clinician before using a supplement.
• Liver disease: people with liver disease are more likely to have serious complications from acetaminophen overdose. [1] See Liver Safety & Supplements.
• Medicines, kidney disease and surgery: specific interactions are not described in the sources we read. Ask a pharmacist; see Medication Interactions and Supplements Before Surgery.
• Quality: supplement contents vary; see Quality Testing and Certifications.

Related pages

See the profile N-Acetylcysteine (NAC), Glutathione Supplements and Antioxidant Safety and Marketing Claims.