N-acetyl cysteine (NAC)

N-acetyl cysteine (NAC)

Definition: *N-acetyl cysteine (NAC)* is a synthetic derivative of the amino acid L-cysteine. It serves as a precursor to glutathione, a key intracellular antioxidant, and has mucolytic, antioxidant, anti-inflammatory, and neuroprotective properties.

Mechanism of Action

Glutathione precursor: NAC provides cysteine for the synthesis of glutathione (GSH), enhancing cellular redox capacity.
Mucolytic effect: Breaks disulfide bonds in mucus glycoproteins, reducing viscosity.
Antioxidant activity: Scavenges free radicals and reactive oxygen species (ROS).
Anti-inflammatory effect: Modulates NF-κB and cytokine production.
Neuroprotective properties: May reduce oxidative stress and excitotoxicity in neurodegenerative and neuropsychiatric conditions.

Clinical Uses

Indication	Use/Effect
Acetaminophen overdose	Antidote—restores hepatic glutathione and prevents hepatotoxicity.
Chronic respiratory diseases	Mucolytic agent in COPD, cystic fibrosis, bronchitis.
Psychiatric disorders	Investigated in schizophrenia, bipolar disorder, OCD.
Neurological disorders	Studied in Parkinson’s, Alzheimer’s, and traumatic brain injury.
Contrast-induced nephropathy	Proposed renal protective effect (evidence inconclusive).

Dosage & Administration

Oral: Common in chronic use (e.g., 600–1800 mg/day).
Intravenous: High-dose protocols for acetaminophen toxicity.
Inhaled (nebulized): For mucolytic purposes.

Safety and Side Effects

Generally well tolerated.
May cause nausea, vomiting, diarrhea, or rare allergic reactions.
IV form may induce anaphylactoid reactions in sensitive individuals.

Research and Emerging Roles

COVID-19: Investigated for reducing oxidative stress and cytokine storm.
Cancer: Explored for its role in modulating redox-sensitive oncogenic pathways.
Prophylactic use: In chronic diseases involving oxidative stress and inflammation.

References

Samuni Y, et al. (2013). The chemistry and biological activities of N-acetylcysteine. *Biochim Biophys Acta*.
Millea PJ. (2009). N-acetylcysteine: multiple clinical applications. *Am Fam Physician*.

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