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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent and an antidote to acetaminophen overdose. It works by replenishing glutathione stores and directly binding to the reactive metabolite of acetaminophen.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce the severity of liver damage.
* **Mucolytic:** To thin and loosen mucus in the airways, aiding in expectoration.
## Adult Dosing
**Acetaminophen Overdose:**
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Infusion:** 50 mg/kg IV infused over 4 hours.
* **Third Infusion:** 100 mg/kg IV infused over 16 hours.
* Maximum total dose for overdose treatment is not strictly defined but should be guided by clinical response and liver function.
* *Note:* Oral dosing is also available, typically 140 mg/kg loading dose followed by 70 mg/kg every 4 hours for 17 doses. Oral administration may be associated with higher rates of nausea and vomiting.
**Mucolytic:**
* **Inhalation:** 3 mL to 5 mL of a 10% or 20% solution nebulized every 3 to 4 hours, or via an aerosol mask. Dosing may be adjusted based on protocol and patient response.
* **Direct Instillation:** 1 to 2 mL of a 10% or 20% solution into the tracheobronchial tree via endotracheal tube every 1 to 4 hours as needed.
## Pediatric Dosing
**Acetaminophen Overdose:**
* Dosing is weight-based and follows the same regimen as adults:
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Infusion:** 50 mg/kg IV infused over 4 hours.
* **Third Infusion:** 100 mg/kg IV infused over 16 hours.
* *Note:* Oral dosing follows the same regimen as adults.
**Mucolytic:**
* **Inhalation:** Dosing is less well-established in neonates and infants. Typically, 1 mL to 2 mL of a 10% or 20% solution nebulized every 4 to 12 hours. Dosing should be guided by local protocol and clinical assessment.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended for mild to moderate renal impairment. Use with caution in severe renal impairment.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended for hepatic impairment when used for acetaminophen overdose, as the goal is to protect the liver.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Acute bronchospasm (for inhaled formulations).
## Adverse Effects
* **Most Common (IV overdose treatment):** Anaphylactoid reactions (rash, pruritus, urticaria, bronchospasm, angioedema, hypotension), nausea, vomiting. These reactions are often infusion-rate dependent.
* **Common (Inhaled):** Bronchospasm, rhinorrhea, nausea, vomiting, stomatitis, chest tightness.
* **Less Common:** Drowsiness, fever, headache, increased sputum viscosity.
## Key Drug Interactions
* **Activated Charcoal:** Can adsorb oral acetylcysteine, potentially reducing its efficacy. Separate administration by at least 1 hour.
* **Nitroglycerin:** May cause additive hypotension.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels.
* Liver function tests (AST, ALT, bilirubin, INR, PT/aPTT).
* Renal function and electrolytes.
* Clinical signs of anaphylactoid reaction during IV infusion.
* **Mucolytic:**
* Airway patency and ease of expectoration.
* Signs of bronchospasm.
## Clinical Pearls
* For acetaminophen overdose, treatment should be initiated empirically if the acetaminophen level is unknown or if it falls within the nomogram treatment line, regardless of time since ingestion.
* IV acetylcysteine infusion rates should be carefully controlled to minimize the risk of anaphylactoid reactions. Premedication with an antihistamine may be considered.
* If bronchospasm occurs with inhaled acetylcysteine, discontinue the treatment and administer a bronchodilator.
* Nausea and vomiting are common with oral acetylcysteine, particularly in children.
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*Disclaimer: This information is intended for clinical use and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before initiating or modifying drug therapy.*
