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*.