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Mucolytic / Antioxidant — COPD / Bronchiectasis Pregnancy: Use with caution — limited data for oral mucolytic use in pregnancy; nebulised use consider risk/benefit

N-Acetylcysteine (Nebulised / Oral)

Brand names: Fluimucil, Parvolex (IV — different indication)

Adult dose

Dose: Oral (mucolytic): 600 mg once daily. Nebulised: 200–300 mg per nebulisation
Route: Oral / Nebulised
Frequency: Once daily (oral); twice daily (nebulised)
Max: 1200 mg/day (oral); 600 mg per nebulisation
Oral NAC used as mucolytic in COPD and bronchiectasis — reduces sputum viscosity, antioxidant effects. Nebulised NAC used in bronchiectasis and CF for mucociliary clearance. Different from IV Parvolex (paracetamol overdose antidote). Evidence for exacerbation prevention in COPD mixed — BRONCHUS trial showed modest benefit.

Paediatric dose

Dose: 200 mg twice or three times daily (children ≥6 years) mg/kg
Route: Oral / Nebulised
Frequency: Twice to three times daily
Max: 600 mg/day
BNFc: mucolytic use in children with bronchiectasis or CF — specialist respiratory guidance. Not the same as IV NAC (Parvolex) for paracetamol OD.

Dose adjustments

Renal

No dose adjustment required

Hepatic

No dose adjustment required

Paediatric weight-based calculator

BNFc: mucolytic use in children with bronchiectasis or CF — specialist respiratory guidance. Not the same as IV NAC (Parvolex) for paracetamol OD.

Clinical pearls

  • BRONCHUS trial (2013): NAC 600 mg OD reduced COPD exacerbations by 22% in patients with moderate-severe COPD not on ICS — modest benefit; GOLD guidelines mention as option in selected patients
  • Nebulised NAC: bronchospasm risk — always pre-treat with salbutamol nebulisation 15 minutes before; particularly important in asthma or reactive airways
  • Antioxidant mechanism: NAC replenishes intracellular glutathione — reduces oxidative stress in airway epithelium; may explain benefit beyond simple mucolysis
  • IV NAC (Parvolex): completely different indication — paracetamol overdose antidote; 300 mg/kg over 21 hours IV; do not confuse with oral/nebulised mucolytic NAC
  • CF: dornase alfa (Pulmozyme) is preferred mucolytic — superior evidence; nebulised NAC used as adjunct or when dornase not tolerated/available
  • NICE: NAC not routinely recommended for COPD — consider only in patients with frequent exacerbations despite optimal inhaled therapy and smoking cessation

Contraindications

  • Hypersensitivity to acetylcysteine
  • Active peptic ulcer (oral form — theoretical risk)

Side effects

  • Nausea (oral)
  • GI disturbance
  • Bronchospasm (nebulised — use with bronchodilator pre-treatment)
  • Rash
  • Stomatitis (oral)

Interactions

  • Activated charcoal — reduces oral NAC absorption (relevant in paracetamol OD context)

Monitoring

  • Exacerbation frequency
  • Sputum volume and viscosity
  • Pulmonary function
  • Bronchospasm (nebulised — first use)

Reference: BNFc; BNF 90; BNFc; BRONCHUS Trial (Decramer et al. Lancet 2005); GOLD 2024; NICE NG115; SPC Fluimucil. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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