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# Acetylcysteine
## Overview
N-acetylcysteine (NAC) is an mucolytic agent and an antidote for acetaminophen overdose. It also has antioxidant properties.
## Primary Indications
* **Acetaminophen overdose:** To prevent or reduce liver damage.
* **Mucolytic:** To thin and loosen mucus in respiratory conditions like COPD, cystic fibrosis, and pneumonia.
## Adult Dosing
* **Acetaminophen overdose:**
* **Loading dose:** 150 mg/kg intravenously (IV) over 1 hour.
* **Second dose:** 50 mg/kg IV over 1 hour, 4 hours after the loading dose.
* **Maintenance dose:** 100 mg/kg IV over 16 hours (total infusion time of 21 hours).
* *Maximum IV dose: 150 mg/kg/hr for loading dose, 12.5 mg/kg/hr for second dose, and 6.25 mg/kg/hr for maintenance dose.*
* *Oral dosing is also an option, with specific protocols varying by institution.*
* **Mucolytic:**
* **Nebulized:** 3% solution, 1-10 mL via nebulizer every 2-6 hours as needed.
* **Oral:** 200-600 mg orally (PO) 1-3 times daily.
## Pediatric Dosing
* **Acetaminophen overdose:** Dosing is the same as adults on a mg/kg basis.
* **Mucolytic:**
* **Nebulized:** 10% solution, 1-5 mL via nebulizer every 2-6 hours as needed. Alternatively, 3% solution, 1-10 mL.
* **Oral:** 50 mg/kg PO up to 2 times daily, maximum 600 mg/day.
## Dose Adjustments
* No dose adjustment is typically required for renal or hepatic impairment, though caution is advised.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
## Adverse Effects
* **IV:** Anaphylactoid reactions (rash, pruritus, angioedema, bronchospasm), flushing, tachycardia, hypotension.
* **Nebulized:** Bronchospasm, stomatitis, nausea, vomiting, rhinorrhea.
* **Oral:** Nausea, vomiting, diarrhea, rash.
## Key Drug Interactions
* **Activated charcoal:** Can reduce the absorption of oral acetylcysteine.
* **Nitroglycerin:** May potentiate the hypotensive effect of nitroglycerin.
## Monitoring
* **Acetaminophen overdose:** Liver function tests (AST, ALT, bilirubin, INR), acetaminophen levels, clinical status.
* **Mucolytic:** Respiratory status, sputum viscosity, effectiveness of airway clearance.
## Clinical Pearls
* IV acetylcysteine for acetaminophen overdose is most effective when started within 8 hours of ingestion.
* Pretreatment with an H1 antagonist (e.g., diphenhydramine) and/or H2 antagonist (e.g., ranitidine) may be considered for patients receiving IV acetylcysteine due to the risk of anaphylactoid reactions.
* For nebulized acetylcysteine, consider co-administration with a bronchodilator to mitigate bronchospasm.
* The smell of acetylcysteine is characteristically sulfurous ("rotten eggs"), which can affect patient adherence.
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*This information is intended for healthcare professionals and does not substitute for current prescribing information. Always consult the official drug monograph and institutional protocols for the most up-to-date and comprehensive guidance.*
