Frequently Asked Questions

Is NAC FDA-approved? Yes. N-acetylcysteine was initially approved by the U.S. Food and Drug administration in 1963.


What are routes of administration of NAC? NAC can be administered orally, intravenously, and can be nebulized for inhalation. Oral NAC is available in liquid and capsule/tablet form.


Is NAC available without a prescription? Yes, depending on the formulation. NAC in solution for IV, oral and inhalational administration need a prescription or are administered in a hospital setting. Oral capsules/tablets and effervescent tablets (not sold in the U.S. currently) can be purchased over-the-counter.


Is NAC a drug or a dietary supplement? Per the FDA letter to LES Labs July 23, 2020, it is a drug:

FDA has concluded that NAC products are excluded from the dietary supplement definition under section 201(ff)(3)(B)(i) of the Act [21 U.S.C. § 321(ff)(3)(B)(i)]. Under this provision, if an article (such as NAC) has been approved as a new drug under section 505 of the Act [21 U.S.C. § 355], then products containing that article are outside the definition of a dietary supplement, unless before such approval that article was marketed as a dietary supplement or as a food. NAC was approved as a new drug under section 505 of the Act [21 U.S.C. § 355] on September 14, 1963. FDA is not aware of any evidence that NAC was marketed as a dietary supplement or as a food prior to that date.


I'm a physician/PA-C/APRN whose patient has early/mild COVID. May I give them/prescribe/recommend NAC without enrolling them in a clinical trial? Yes. Because NAC is already FDA-approved and available over-the-counter, using shared decision-making you may recommend that your patient take [oral] NAC.


Which study to date makes a case for use of NAC in viral illnesses like COVID-19? De Flora, S.; Grassi, C.; Carati, L. (1 July 1997). "Attenuation of influenza-like symptomatology and improvement of cell-mediated immunity with long-term N-acetylcysteine treatment". European Respiratory Journal. 10 (7): 1535–1541. doi:10.1183/09031936.97.10071535. PMID 9230243

This study looked at use of NAC in attenuating symptoms of influenza.

NACinCOVID Review of De Flora et al (NAC and influenza).pptx