N-Acetylcysteine and Acetylcysteine Are the Same Drug
N-acetylcysteine (NAC) and acetylcysteine are identical compounds—there is no clinical difference between them. The "N-" prefix simply denotes the chemical structure where an acetyl group is attached to the nitrogen of the amino acid L-cysteine 1.
Chemical Identity and Nomenclature
- Both terms refer to the same molecule with the chemical formula C5H9NO3S and molecular weight of 163.2 1
- The compound is the N-acetyl derivative of the naturally-occurring amino acid L-cysteine 1
- In clinical practice and medical literature, the terms are used interchangeably 2, 3
Mechanism of Action for Mucus Management
The drug works by cleaving disulfide bonds in mucoproteins, which reduces the viscosity of respiratory secretions and makes thick mucus easier to clear from the airways 3, 4.
- This mucolytic action occurs regardless of which name is used on the label 5
- The drug also has bronchorrheic effects when aerosolized and expectorant/mucoregulator actions when given orally 5
Available Formulations and Routes
The same compound is available in multiple formulations 1:
- Inhaled/nebulized: 20% solution (200 mg/mL) for direct airway administration 1
- Oral: Tablets or solution, with high-dose therapy (600 mg twice daily) showing greater efficacy for COPD exacerbations 3, 4
- Intravenous: For situations requiring IV administration, demonstrating significant improvement in sputum viscosity and expectoration difficulty 6
Clinical Applications for Mucus Disorders
For patients with moderate to severe COPD and recurrent exacerbations despite optimal inhaled therapy, oral N-acetylcysteine 600 mg twice daily is recommended 2, 3.
- This high-dose regimen reduces exacerbation rates (rate ratio 0.69) and hospitalizations (risk ratio 0.76), requiring treatment of 25 patients to prevent one hospitalization 2
- The drug is indicated for abnormal, viscid, or inspissated mucous secretions in chronic bronchopulmonary disease, acute bronchitis, cystic fibrosis complications, and atelectasis due to mucous obstruction 1
Important Clinical Caveats
- Inhaled N-acetylcysteine lacks evidence for chronic use: The Cystic Fibrosis Foundation found insufficient evidence to recommend chronic inhaled therapy, with no demonstrated clinical benefit or lung function improvement 7
- The drug appears more effective in moderate COPD (GOLD II) compared to severe disease (GOLD III) 3
- While effective at reducing exacerbations, it has not been shown to significantly impact mortality 3
- Common side effects include nausea, vomiting, and diarrhea, though the drug is generally well-tolerated 3, 8