N-acetyl Cysteine (nac)
OTHER NAME(S): N-acetyl cysteine (NAC), N-acetyl-L-cysteine, N-acetylcysteine
Overview
N-acetyl cysteine (NAC) is available over the counter as a dietary supplement. It is used for various reasons, although its benefits are not well defined. Common side effects may include diarrhea, nausea, vomiting, or an upset stomach. Before taking N-acetyl cysteine, make sure to tell your health care provider about any health conditions you have or medicines you are taking.
Uses
What is N-acetyl cysteine (NAC) used for?
N-acetyl cysteine (NAC) is used for many different reasons as a dietary supplement, although its benefits are not well defined. Some common reasons that people use N-acetyl cysteine as a dietary supplement include the following.
- Chronic lung conditions, such as chronic obstructive pulmonary disease (COPD)
- Depression
- Liver health
- To manage side effects of cancer treatments
- To support the immune system
Note: The FDA has not reviewed N-acetyl cysteine dietary supplements for safety and effectiveness. Learn more about dietary supplements here.
Acetylcysteine is also available as a prescription product that is used for acetaminophen (Tylenol) overdose or for certain lung conditions. See Acetylcysteine and Acetylcysteine inhaled for more information.
How does N-acetyl cysteine work (mechanism of action)?
N-acetyl cysteine is a form of cysteine, an amino acid that occurs naturally in the body. N-acetyl cysteine acts as an antioxidant and may also help to reduce inflammation (swelling). Taking N-acetyl cysteine can also increase levels of cysteine, which has many important functions in the body.
In some long-term lung conditions, such as COPD or cystic fibrosis, mucus builds up in the lungs. N-acetyl cysteine may help break up this mucus and reduce inflammation, making it easier to breathe. But its benefits for these uses are not well defined. Although there are many studies of N-acetyl cysteine for these lung conditions, some studies show that it helps, while others show that it has no effect.
N-acetyl cysteine is used for many other reasons, but its benefits are not well defined.
How should I store N-acetyl cysteine?
You should store N-acetyl cysteine according to the product label. Most dietary supplements should be kept in a cool, dry place that is out of the reach of children and pets and not in direct sunlight.
Side Effects
What are the most common side effects of N-acetyl cysteine?
The most common side effects of N-acetyl cysteine are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.
- Diarrhea
- Nausea or vomiting
- Upset stomach
- Rash
There may be other side effects of N-acetyl cysteine that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.
What are the serious side effects of N-acetyl cysteine?
While less common, the most serious side effects of N-acetyl cysteine are described below, along with what to do if they happen.
Severe Allergic Reactions. N-acetyl cysteine may cause allergic reactions, which can be serious. Stop taking N-acetyl cysteine and get help right away if you have any of the following symptoms of a serious allergic reaction.
- Breathing problems or wheezing
- Racing heart
- Fever or general ill feeling
- Swollen lymph nodes
- Swelling of the face, lips, mouth, tongue, or throat
- Trouble swallowing or throat tightness
- Itching or skin rash
- Bumps on the skin called hives that can be red, pink, white, or brown, depending on your skin tone
- Nausea or vomiting
- Dizziness, feeling lightheaded, or fainting
- Stomach cramps
- Joint pain
Precautions
Who should not use N-acetyl cysteine?
Allergies to Ingredients. People who are allergic to any of the following should not take N-acetyl cysteine.
- Acetylcysteine
- N-acetyl cysteine (NAC)
- Any of the ingredients in the specific product
Your pharmacist can tell you all of the ingredients in the specific N-acetyl cysteine products they stock.
What should I know about N-acetyl cysteine before using it?
N-acetyl cysteine that comes as a dietary supplement cannot be marketed to treat or cure a disease.
Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.
Keep N-acetyl cysteine out of the reach of children.
N-acetyl cysteine dietary supplements may have a strong smell or taste. Although this smell or taste may be unpleasant to some people, it is normal for N-acetyl cysteine products.
If you are taking N-acetyl cysteine as a gummy, chew the gummy well before swallowing. If you are taking a liquid N-acetyl cysteine product, use an accurate measuring device to measure your dose. A household spoon is not an accurate measuring device and may cause you to take the wrong dose. Ask your pharmacist what measuring device to use.
The FDA has not tested N-acetyl cysteine dietary supplements to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.
What should I tell my health care provider before using N-acetyl cysteine?
Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if N-acetyl cysteine is right for you.
In particular, make sure that you discuss any of the following.
Other Medicines and Supplements.N-acetyl cysteine may interact with other medicines and supplements. Before taking N-acetyl cysteine, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.
Pregnancy. It is not known if or how N-acetyl cysteine could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.
Breastfeeding. It is not known if N-acetyl cysteine passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.
Interactions
Does N-acetyl cysteine interact with foods or drinks?
There are no known interactions between N-acetyl cysteine and foods or drinks.
It is unknown if drinking alcohol will affect N-acetyl cysteine.
Does N-acetyl cysteine interact with medicines (drug interactions)?
Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.
In particular, make sure that you discuss if you are using any of the following before taking N-acetyl cysteine.
- A nitrate – such as nitroglycerin (Nitro-Dur, NitroMist, Nitrostat, and others), isosorbide dinitrate (Isordil), or isosorbide mononitrate – which is a medicine used to prevent or treat short-lasting chest pain caused by a type of heart disease
- Pirfenidone (Esbriet), which is a medicine used for idiopathic pulmonary fibrosis
The interactions between N-acetyl cysteine and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with N-acetyl cysteine is incomplete. Always check with your health care provider before taking N-acetyl cysteine with any medicines.
Dosing
What should I do if I accidentally use too much N-acetyl cysteine?
If you or someone else has used too much N-acetyl cysteine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.
N-acetyl cysteine dietary supplements come in many different forms. Read the product label closely and speak with a health care provider about how to use N-acetyl cysteine safely. Do not take double or extra doses, even if you miss a dose.
References
- Drug Safety: “Safety of N-acetylcysteine at high doses in chronic respiratory disease: a review.”
- Journal of the American College of Cardiology: “Effect of transdermal nitroglycerin or N-acetylcysteine, or both, in the long-term treatment of unstable angina pectoris.”
- Memorial Sloan Kettering: “N-acetylcysteine, Purported Benefits, Side Effects & More.”
- National Cancer Institute NCI Drug Dictionary: “Acetylcysteine.”
- FDA: “FDA Releases Final Guidance on Enforcement Discretion for Certain NAC Products,” “Guidance for Industry: Policy Regarding N-acetyl-L-cysteine.”