mucolytic

Acetylcysteine (N-Acetylcysteine)

Mucomyst / Acetadote (IV)

Route: inhaled (SVN) · IV · oral
Onset: Mucolytic: 1 minute; maximum effect 5–10 minutes
Duration: 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)

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

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)

All Drugs

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