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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that facilitates the removal of mucus from the respiratory tract. It is also the antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver damage.
* **Mucolytic:** To thin and loosen mucus secretions in conditions such as bronchitis, emphysema, and cystic fibrosis.
## Adult Dosing
### Acetaminophen Overdose
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Dose:** 50 mg/kg IV infused over 16 hours.
* **Subsequent Doses:** If acetaminophen levels remain elevated or liver enzymes increase, follow local protocol. Some protocols recommend continuing infusions at 12.5 mg/kg/hr or adjusting doses based on acetaminophen levels.
* **Oral Protocol (less common):** 140 mg/kg orally as a loading dose, followed by 70 mg/kg orally every 4 hours for 17 doses.
* **Maximum Doses:** Dosing is typically weight-based; high risk of anaphylactoid reactions with rapid IV infusion.
### Mucolytic
* **Nebulization:** 1-10 mL of 10% or 20% solution, or 5-10 mL of 20% solution, every 2-6 hours as needed.
* **Direct Instillation:** 1-2 mL of 10% or 20% solution into tracheostomy or endotracheal tube every 1-4 hours.
* **Oral:** 200 mg orally twice daily up to 600 mg twice daily.
## Pediatric Dosing
### Acetaminophen Overdose
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Dose:** 50 mg/kg IV infused over 16 hours.
* **Subsequent Doses:** As per adult protocol, adjusted for weight.
* **Oral Protocol (less common):** 140 mg/kg orally as a loading dose, followed by 70 mg/kg orally every 4 hours for 17 doses.
### Mucolytic
* **Nebulization (under 6 years):** 1-2 mL of 20% solution or 2-4 mL of 10% solution every 2-6 hours.
* **Nebulization (over 6 years):** 5-10 mL of 20% solution or 10 mL of 10% solution every 2-6 hours.
* **Oral:** 50 mg/kg/day divided into 2-3 doses, up to 600 mg/day.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment due to the primary use in acute settings for overdose, or generally well-tolerated doses for mucolytic therapy. However, caution is advised in severe hepatic impairment for mucolytic use.
## Contraindications
* Hypersensitivity to acetylcysteine.
## Adverse Effects
* **Common (IV for overdose):** Anaphylactoid reactions (rash, urticaria, angioedema, bronchospasm, dyspnea, nausea, vomiting), flushing, tachycardia.
* **Common (Nebulized):** Bronchospasm, nausea, vomiting, stomatitis, rhinorrhea.
* **Other:** Fever, headache, dizziness.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its systemic absorption. Separate administration by at least 2 hours (or 1 hour if charcoal contains sorbitol).
## Monitoring
* **Acetaminophen Overdose:**
* Acetaminophen serum levels.
* Liver function tests (AST, ALT, bilirubin, INR).
* Renal function and electrolytes.
* Blood glucose.
* Clinical signs of anaphylactoid reaction.
* **Mucolytic:**
* Respiratory status (e.g., auscultation, effectiveness of secretion removal).
* Potential for bronchospasm.
## Clinical Pearls
* The risk and severity of anaphylactoid reactions with IV acetylcysteine for acetaminophen overdose can be minimized by slow infusion rates and premedication (e.g., antihistamines, corticosteroids) if indicated per local protocol, especially for those with a history of asthma or previous reaction.
* Dilute IV acetylcysteine to avoid phlebitis.
* Bronchospasm can occur with nebulized acetylcysteine; a beta-agonist bronchodilator may be administered beforehand or concurrently.
* The distinctive sulfurous ("rotten egg") odor of acetylcysteine can cause nausea and vomiting.
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**Disclaimer:** Always verify current prescribing information and local protocols before administering any medication. This information is intended for healthcare professionals and is not a substitute for clinical judgment.
