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NAC Supplements: The Good, The Bad, The Buzz

Updated February 2023: Since our original post (below) in 2021, there have been several developments regarding the FDA’s views on NAC supplements. Initially, concerns arose due to exaggerated marketing claims by retailers, causing Amazon to preemptively pull NAC-containing supplements from its online store. In 2022, the FDA provided interim guidance that suggested it may invoke the “exclusion clause,” which would prevent NAC-containing products from being legally marketed as supplements because NAC was first approved as a drug in 1963. As a result, two citizen petitions were filed by the Natural Products Association and the Council for Responsible Nutrition in an effort to encourage the FDA to reconsider its position. 

Although the FDA denied the claims, in August 2022, it released its final guidance regarding NAC-containing supplements, noting that because NAC has been safely used for more than 30 years in dietary supplements, the FDA will exercise enforcement discretion and only take action if it identifies safety concerns in specific NAC-containing dietary supplements. This guidance paved the way for retailers to resume selling supplements, and Amazon has since relisted several NAC-containing products.

Aside from the NAC supplement debate, very recent evidence from Yale has indicated that NAC may also be effective at treating COVID-related brain fog. This is supported by early COVID research that indicated that brain fog and other long COVID symptoms may manifest due to a glutathione deficiency. Because NAC is metabolized into cysteine, it can help replenish the body’s stores of glutathione, which is synthesized from cysteine and glutamate. Although this research is still in its infancy, it shows that prescribing NAC may help alleviate COVID-related symptoms. 

Should prescribers decide that NAC is appropriate for their patient, VLS Pharmacy & New Drug Loft is here to help and can compound it for a variety of administration routes.

Original post from June 22, 2021: N-acetylcysteine (NAC) is both a medication and a dietary supplement. As a medication, NAC is an effective antidote for acetaminophen overdose, which can be life threatening. It’s also commonly used to break up mucus in the lungs for those suffering from respiratory conditions. NAC is taken as a dietary supplement to support the immune system, as it is a precursor to glutathione and regulates the neurotransmitter glutamate while reducing oxidative damage to tissues across the body.

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NAC has robust research in terms of efficacy. Below, we review the good, the bad, and the current industry buzz around NAC. 

N-acetylcysteine (NAC): An Overview

NAC is the initialism for compounds N-acetyl-cysteine, N-acetylcysteine, and N-acetyl cysteine. It is a precursor for cysteine, an amino acid that enables antioxidant activity in the body. Cysteine is derived from methionine and serine, so when an individual is low on these amino acids, they may need to boost their cysteine levels by taking NAC supplements. Cysteine exists in protein-rich foods like eggs, chicken, turkey, yogurt, and legumes. NAC also moderates the glutamatergic system.

The use of NAC in patient care began with its patenting in 1960. In 1968, medical professionals began using NAC as a treatment option. Currently, the World Health Organization lists NAC as an Essential Medicine because of its role in treatment for acetaminophen poisoning. NAC can be administered in three ways: oral tablet/capsule, IV fluid, or inhaled as a gas.  While healthcare professionals often prescribe NAC as a medication, the general public is able to purchase its supplement forms. 

N-acetylcysteine (NAC): The Good

Research purports that NAC is effective in the treatment of liver toxicity and chronic lung disease (Mohkarti et. al., 2017). The results of previous studies may indicate its usefulness in preventing cancer and treating depression as well as HIV/AIDs, though more research is needed to confirm these indications (Mohkarti et. al., 2017). Overall, NAC restores the powerful antioxidant glutathione, which enhances oxidative balance in the body. In this way, NAC supports the immune system and helps break down toxins — toxins that impact internal organs and overall well-being.

The primary reason why healthcare professionals prescribe NAC for patients — and why NAC is often in high demand at healthcare facilities such as emergency rooms — is in the event of acetaminophen or paracetamol poisoning (Ershad et. al., 2021). When an individual overdoses on acetaminophen or paracetamol, NAC protects the liver and kidneys from the toxic levels of N-acetyl-p-benzoquinone imine (NAPQI), a minor metabolite. Generally, glutathione, an antioxidant, helps to break down NAPQI. However, in the event of an overdose, the body’s natural glutathione reserves cannot overcome the high toxin levels. When NAC enters the mix, it replenishes glutathione and protects vital organs from the impact of toxins by bonding to dangerous oxidants. The use of NAC as a medication is most effective when administered within a 10-hour window post-overdose.

Additionally, NAC is used in treatment of chronic lung disease (Mohkarti et. al., 2017). NAC, when inhaled, reduces disulphide bonds and converts them into sulfhydryl bonds, which decreases mucus in the respiratory system. For this reason, clinicians utilize NAC when executing tracheostomy care as a mucolytic or when patients have a collapsed lung due to mucus levels. Again, NAC is an antecedent to glutathione, an antioxidant helpful to treat chronic lung diseases and bronchitis, in the respiratory system.

Recent studies indicate that NAC may be helpful in treating psychiatric disorders such as depression, addiction, grooming disorders, OCD, or schizophrenia (Dean et. al., 2011). NAC modulates the neurotransmitters glutamate and dopamine, which are both important for brain function. NAC may also decrease neuroinflammation, which often impacts cognition (Skvarc et. al., 2017). More studies are needed to confirm NAC’s efficacy in this area.

In our pharmacies, we consistently hear from our customers that NAC is something they prefer for immune enhancing benefits. There is evidence in this preference as NAC’s role in detoxification via its connection with glutathione means that its main benefit, when taken as a supplement, is the destruction of free radicals in the body (Sansone et. al., 2011). In a healthcare culture that focuses on prevention, people find it appealing to take a supplement that promotes a strong immune system. While many individuals create enough cysteine through diet, augmenting these reserves ensures that there will be plenty of antioxidants when needed in the face of toxification.

N-acetylcysteine (NAC): The Bad

While the NAC research demonstrates efficacy for NAC as a treatment for acetaminophen or paracetamol overdoses and respiratory conditions, additional research is needed to agree upon NAC’s efficacy in treating other health conditions.

There may be side effects of taking NAC, including but not limited to:

  • Urticaria
  • Itchiness or rashes
  • Hypotension
  • Nausea

Due to the risk of potential side effects and possible interactions with medications, NAC should not be taken with nitroglycerin, so it’s important for individuals to check with a healthcare professional (including their pharmacist) prior to taking NAC as a dietary supplement.

As with many dietary supplements, the fine line between supplement and medication positions retailers in a conundrum. Because NAC is a medication commonly used in the treatment of health conditions, its dual role as a dietary supplement — and something that is available for anyone to buy — becomes questionable. The Food and Drug Administration (FDA) advocates for regulation over dietary supplement retailer claims, ensuring that all claims made by these retailers are scientifically-based and accurate. Many companies that sold NAC as a dietary supplement (or included NAC in other products) boasted that their products prevented cancer, cured hangovers, and created bullet-proof immune systems. For this reason, Amazon created a buzz when deciding to pull NAC dietary supplements out of their stores (including Whole Foods).

While NAC is wrapped up in hefty arguments between the FDA and retailers, those arguments focus on marketing, not the drug’s usefulness in treating the intended medical conditions. NAC is still available for purchase and is often used as a dietary supplement. However, determining the exact dose and whether it is appropriate for a specific individual, are keys to benefitting from its health impacts.

N-acetylcysteine (NAC): Dosage Forms & Clinical Oversight

There are different ways to take NAC, including inhalant, intravenously, and orally. The best way to take NAC depends on the situation and intended goal. Inhalants are best used for mucolytic care, while IV therapy is effective for acetaminophen or paracetamol overdoses. NAC is also available in effervescent tablets, oral tablets, and capsules, depending on its reason for use. When an individual needs NAC — whether for a medical treatment or for a dietary supplement — getting the right dose matters. To ensure that both the dosage and dosage form is appropriate, NAC should be taken under the guidance of a licensed medical professional.


Reach out to our team to learn about best practices and to partner with our experts on custom compounded medications for your patients. 

All medications from VLS Pharmacy and New Drug Loft are prepared in a lab that follows safety and quality standards per our status as a 503A pharmacy.



Covid-19 Vaccine at VLS Pharmacy

VLS Pharmacy is currently administering the Moderna Vaccine by appointment only to those age 18 and older. If appointments are unavailable, please check back frequently as New York State is systematically allocating vaccines. As we receive more vaccines, more spots will open. Please note: we CANNOT book your appointment over the phone due to the screening requirements.

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