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N-Acetylcysteine (NAC)

Summary: N-acetylcysteine (NAC) is a medication that may possibly be helpful in the treatment of various mental health conditions.
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What is N-Acetylcysteine?

N-acetylcysteine (NAC) comes from the amino acid L-cysteine. Amino acids are the building blocks of proteins. NAC is a glutathione precursor that effectively replenishes brain glutathione, which is an antioxidant.

NAC has been used for decades to treat acetaminophen (aka paracetamol) overdose.

It turns out that NAC may also be helpful in other conditions where there is oxidative stress such as apoptosis, mitochondrial dysfunction, neuroinflammation, as well as glutamate and dopamine dysregulation.

What Might It Be Helpful For?

Evidence suggests it may be helpful for various brain conditions (Deepmala, 2015):

  • Alzheimer disease
  • Mood conditions such as depression and bipolar;
  • Trichotillomania, nail biting, skin picking, obsessive-compulsive disorder (OCD)
  • Autism;
  • Cocaine and cannabis addiction,
  • Schizophrenia,
  • Drug-induced neuropathy.

There is preliminary evidence for the following conditions, though more studies are required (Deepmala, 2015):

  • Anxiety,
  • Attention deficit hyperactivity disorder
  • Mild traumatic brain injury

Evidence does not support the use of NAC with gambling, methamphetamine and nicotine addictions and amyotrophic lateral sclerosis.

As research is limited however, it is generally not recommended unless standard treatments have been ineffective.

What Dosages?




Treatment resistant obsessive compulsive disorder (OCD)

Adults: Start 1000 mg twice daily x 1-week, then increase to 1500 mg twice daily

Couto, 2018

Adolescents: Start 600 mg twice daily and move up to 1200 mg twice daily

Arnold, 2020

Adjunctive treatment in bipolar depression

Adults: 1000 mg twice daily

Berk et al., 2011


Adults: 600-1200 mg twice daily

Grant, 2009

Most studies on NAC have been in adults. Few (if any studies) have looked at dosages for children and adolescents.

Where to Find it?

NAC can be found in drug stores, natural health foods stores and online retailers.

As NAC is a supplement, note that NAC is not regulated in the same manner as standard conventional medications might be. There may be significant variations between manufacturers in terms of purity and the active ingredient.


Arnold, P. CACAP Conference: Group 1 Discussion with Dr. Paul Arnold, 2020.

Couto JP, Moreira R. Oral N-acetylcysteine in the treatment of obsessive compulsive disorder: a systematic review of the clinical evidence. Prog Neuropsychopharmacol Biol Psychiatry


Deepmala D et al.: Clinical trials of N-acetylcysteine in psychiatry and neurology: A systematic review. Neuroscience and Biobehavioural Reviews. 2015; 55: 294-321.

Dean O et al.: N-acetylcysteine in psychiatry: current therapeutic evidence and potential mechanisms of action. J Psychiatry Neurosci. 2011 Mar; 36(2): 78–86.

Grant J et al.: N-acetylcysteine, a glutamate modulator, in the treatment of trichotillomania: a double-blind, placebo-controlled study. Arch Gen Psychiatry. 2009 Jul;66(7):756-63. doi: 10.1001/archgenpsychiatry.2009.60.

About this Article

Written by the health professionals at the Children’s Hospital of Eastern Ontario (CHEO) in Ottawa, Ontario, Canada. Special thanks to Dr. Paul Arnold for information about NAC dosages in adolescents.

Conflicts of interest: The authors have no competing interests to declare.

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Information in this pamphlet is offered ‘as is' and is meant only to provide general information that supplements, but does not replace the information from your health provider. Always contact a qualified health professional for further information in your specific situation or circumstance.

Date Posted: Sep 18, 2020
Date of Last Revision: Sep 18, 2020

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