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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucus, reducing its viscosity. It also serves as an antidote for acetaminophen overdose by replenishing hepatic glutathione stores.
## Primary Indications
* **Acetaminophen overdose:** To prevent or reduce liver toxicity.
* **Mucolytic:** To thin mucus in conditions such as chronic bronchitis, emphysema, cystic fibrosis, and pneumonia.
## Adult Dosing
**Acetaminophen Overdose:**
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Dose:** 50 mg/kg IV infused over 16 hours.
* **Third Dose:** 100 mg/kg IV infused over the next 16 hours (total infusion time 33 hours).
* Protocols may vary. Dosing may be adjusted based on acetaminophen levels and time since ingestion.
**Mucolytic (Oral/Nebulized):**
* **Oral:** 200 mg to 400 mg two to three times daily. Maximum dose not clearly established but typically not to exceed 1200 mg daily.
* **Nebulized:** 1 mL to 2 mL of a 10% or 20% solution (100 mg/mL to 200 mg/mL) every 3-4 hours as needed. Or 600 mg once daily via nebulizer.
## Pediatric Dosing
**Acetaminophen Overdose:**
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Dose:** 50 mg/kg IV infused over 16 hours.
* **Third Dose:** 100 mg/kg IV infused over the next 16 hours (total infusion time 33 hours).
* The initial loading dose should not exceed 150 mg/kg.
**Mucolytic (Nebulized):**
* **Nebulized:** 1 mL to 2 mL of a 10% or 20% solution (100 mg/mL to 200 mg/mL) every 3-4 hours as needed.
## Dose Adjustments
No specific dose adjustments are routinely required for hepatic or renal impairment, but caution is advised.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active bronchospasm (for nebulized use).
## Adverse Effects
* **IV:** Anaphylactoid reactions (rash, pruritus, angioedema, bronchospasm, dyspnea), hypotension, tachycardia, nausea, vomiting.
* **Nebulized:** Bronchospasm, stomatitis, rhinorrhea, nausea, vomiting.
* **Oral:** Nausea, vomiting, diarrhea, stomatitis.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its absorption. Administer charcoal at least 1 hour before or several hours after oral acetylcysteine.
* **Nitroglycerin:** May potentiate hypotensive effects and vasodilation.
## Monitoring
* **Acetaminophen Overdose:** Serum acetaminophen levels, liver function tests (AST, ALT, bilirubin), prothrombin time, glucose, electrolytes, renal function, and clinical signs of liver toxicity.
* **Mucolytic:** Respiratory status, sputum volume and consistency, and for signs of bronchospasm.
## Clinical Pearls
* For IV administration in acetaminophen overdose, it is crucial to follow established protocols, as dosing and infusion rates are critical.
* The smell of acetylcysteine is characteristically unpleasant (sulfurous); this may affect patient adherence with oral or nebulized formulations.
* Nebulized acetylcysteine can sometimes cause bronchospasm. Co-administration with a bronchodilator may be considered.
* Rapid IV infusion can lead to anaphylactoid reactions. Slowing the infusion rate may help manage these reactions.
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*Please consult the most current prescribing information and institutional protocols for definitive guidance.*
