Acetylcysteine

# Acetylcysteine ## Overview N-acetylcysteine (NAC) is a precursor to glutathione, used primarily as an antidote for acetaminophen overdose and as a mucolytic agent. It possesses antioxidant properties. ## Primary Indications - Acetaminophen (paracetamol) overdose (IV or oral) - Mucolytic therapy (e.g., chronic obstructive pulmonary disease, cystic fibrosis) - Prevention of contrast-induced nephropathy (limited evidence; not universally recommended) ## Adult Dosing ### Acetaminophen Overdose – IV Protocol (weight-based) Exact dosing **depends on local protocol** (e.g., 3-bag or 2-bag regimen). Common 3-bag (Rumack–Matthew) protocol: - **Loading**: 150 mg/kg in 200 mL D5W over 1 hour - **Second infusion**: 50 mg/kg in 500 mL D5W over 4 hours - **Third infusion**: 100 mg/kg in 1000 mL D5W over 16 hours ### Acetaminophen Overdose – Oral Protocol - **Loading**: 140 mg/kg - **Maintenance**: 70 mg/kg every 4 hours for 17 total doses ### Mucolytic - **Oral**: 200–400 mg three times daily - **Nebulized**: 3–5 mL of 10% or 20% solution every 6–8 hours (or as directed) ## Pediatric Dosing - **Acetaminophen overdose (IV)**: Same weight-based dosing as adults. Maximum weight for dosing: often capped at 100 kg (use actual body weight if <100 kg, protocol weight if >100 kg per local rules). - **Acetaminophen overdose (oral)**: Loading 140 mg/kg, then 70 mg/kg every 4 hours for 17 doses. - **Mucolytic (nebulized)**: Children ≥2 years: 3–5 mL of 10% solution every 6–8 hours; adjust based on clinical response. ## Dose Adjustments - **Renal impairment**: No adjustment required. - **Hepatic impairment**: No specific dose adjustment; monitor for adverse effects. - **Obesity**: Generally use actual body weight for overdose, but confirm local protocol (some cap at 100 kg for IV infusion). ## Contraindications - Hypersensitivity to acetylcysteine or any component - Asthma (relative caution; increased risk of bronchospasm with inhaled use) - Severe gastrointestinal obstruction (oral mucolytic use) ## Adverse Effects - **Common**: Nausea, vomiting, rash, flushing (especially with IV loading; may slow infusion rate) - **Serious**: Anaphylactoid reactions (IV), bronchospasm (inhalation), angioedema - **Other**: Urticaria, pruritus, hypotension ## Key Drug Interactions - **Nitroglycerin**: Increased risk of hypotension (additive vasodilation) - **Activated charcoal**: May adsorb oral NAC if given simultaneously; separate administration by 1–2 hours (though often given together in overdose) - **Carbamazepine, methotrexate, phenytoin**: Theoretically reduced efficacy of these drugs (limited evidence) ## Monitoring - **Acetaminophen overdose**: Acetaminophen concentration, liver function tests (ALT/AST), INR, renal function, acid-base status - **IV infusion**: Observe for hypersensitivity reactions (especially during first 15 minutes); have resuscitation equipment available - **Mucolytic therapy**: Clinical response (sputum clearance) and pulmonary function ## Clinical Pearls - Intravenous NAC can be safely given to pregnant patients with acetaminophen overdose. - For acute ingestion, NAC is most effective if started within 8 hours; benefit persists even after 24 hours. - Oral NAC may cause vomiting; antiemetics (e.g., ondansetron) are often required. - The IV three-bag protocol can cause fluid overload in patients with heart failure; consider adjusting volume or using the oral route. - Nausea and flushing during IV loading are common; slow the infusion rate (e.g., over 2 hours) if tolerated. --- **Disclaimer**: This information is for educational reference only. Always verify current dosing guidelines, local protocols, and prescribing information from authoritative sources (e.g., FDA labeling, national formularies, or institutional guidelines). Clinical decisions must consider individual patient factors and evolving evidence.