Learning Center/Pharmacology/Acetylcysteine (N-Acetylcysteine) Acetylcysteine (N-Acetylcysteine)
Mucomyst / Acetadote (IV)
mucolyticinhaled (SVN) · IV · oralOnset: Mucolytic: 1 minute; maximum effect 5–10 minutesDuration: Mucolytic: 2–3 hours per treatment
Mechanism of Action
Free thiol group cleaves disulfide bonds in mucus glycoproteins → reduces mucus viscosity. As antidote: replenishes glutathione stores → prevents hepatotoxicity from NAPQI (acetaminophen toxic metabolite).
Dosing
Adult
Mucolytic SVN: 3–5 mL of 10% or 20% solution (diluted) q4–8h. IV (acetaminophen OD): 150 mg/kg IV over 60 min, then 50 mg/kg over 4 hr, then 100 mg/kg over 16 hr
Pediatric
Same weight-based IV protocol for acetaminophen OD
Indications
- Mucolytic: thick/viscous secretions (CF, bronchiectasis, atelectasis)
- Acetaminophen overdose antidote (IV and oral)
- Contrast-induced nephropathy prophylaxis (controversial)
- Meconium ileus equivalent (CF)
Contraindications
- Hypersensitivity to acetylcysteine
- Use with caution in asthma (inhaled form may cause bronchospasm)
Side Effects
- Bronchospasm (inhaled — most clinically important)
- Nausea/vomiting (oral or IV)
- Stomatitis
- Rhinorrhea (inhaled)
- Anaphylactoid reaction (IV — especially at start of infusion)
- Unpleasant sulfur (rotten egg) odor
Monitoring Parameters
- Breath sounds and work of breathing (bronchospasm risk)
- Liver function tests (acetaminophen OD protocol)
- SpO2 during nebulization
- Anaphylactoid signs with IV: rash, urticaria, bronchospasm
Drug Interactions
- Activated charcoal (adsorbs oral acetylcysteine — administer separately)
- Nitroglycerin (possible severe hypotension with IV NAC)
Clinical Pearls
- ALWAYS pre-treat with a bronchodilator (albuterol) before inhaled acetylcysteine to prevent bronchospasm
- 20% solution must be diluted 1:1 with NS or sterile water for nebulization
- 10% solution can be nebulized directly
- Dual role: mucolytic AND acetaminophen antidote — high-yield exam topic
- IV form (Acetadote) — anaphylactoid reactions most common in first 30 minutes; slow infusion rate
- Has a distinctive sulfur odor — warn patients
Mnemonic
💡 NAC = N-Acetylcysteine = Needs A Co-bronchodilator (always pre-treat with albuterol)
NBRC High-Yield
- Mucolytic AND acetaminophen antidote — must know both uses
- Always administer a bronchodilator before inhaled acetylcysteine
- 20% solution must be diluted before nebulization; 10% used as-is
- IV anaphylactoid reactions most common in first 30 min — slow rate
- Mechanism: breaks disulfide bonds in mucus