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# Acetylcysteine
## Overview
Acetylcysteine (N-acetylcysteine, NAC) is an antidote for acetaminophen overdose and a mucolytic agent.
## Primary Indications
* **Acetaminophen Overdose:** Antidote to prevent or treat acetaminophen-induced hepatotoxicity.
* **Mucolytic:** Liquefies thick mucus in respiratory conditions (e.g., cystic fibrosis, COPD, pneumonia).
## Adult Dosing
**Acetaminophen Overdose:**
* **IV:** Typically a 3-bag (or 4-bag) protocol over 72 hours.
* Loading dose: 150 mg/kg infused over 60 minutes.
* Second dose: 50 mg/kg infused over 60 minutes, 4 hours after the loading dose.
* Third dose: 100 mg/kg infused over 16 hours.
* Maximum dose: Continuous infusion of 12.5 g over 72 hours.
* **PO:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses. (Less commonly used due to lower efficacy and GI intolerance).
**Mucolytic:**
* **Inhaled:** 1-10 mL of 10% or 20% solution via nebulizer every 2-6 hours, as needed. Higher concentrations may be better tolerated.
* **PO:** 200 mg twice daily to 600 mg three times daily.
## Pediatric Dosing
**Acetaminophen Overdose:**
* **IV:** Dosing is weight-based, following the same protocol as adults (150 mg/kg, 50 mg/kg, 100 mg/kg). Concentrations and infusion rates may need adjustment based on the child's weight to avoid fluid overload. Consult specific pediatric protocols.
* **PO:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
**Mucolytic:**
* **Inhaled:** 1-10 mL of 10% or 20% solution via nebulizer every 2-6 hours. Dosing is less standardized; consider patient tolerance and response.
## Dose Adjustments
No dose adjustment is typically required for renal or hepatic impairment for acetaminophen overdose. For mucolytic use, adjustments may be based on patient tolerance and response.
## Contraindications
* Hypersensitivity to acetylcysteine.
* Active bronchospasm (for inhaled use, though benefits may outweigh risks).
## Adverse Effects
* **IV (Acetaminophen Overdose):** Anaphylactoid reactions (rash, urticaria, angioedema, bronchospasm, dyspnea, hypotension), nausea, vomiting.
* **Inhaled:** Bronchospasm, airway irritation, nausea, vomiting, stomatitis.
* **PO:** Nausea, vomiting, diarrhea, abdominal pain.
## Key Drug Interactions
* **Activated Charcoal:** May bind to acetylcysteine if given orally, potentially reducing absorption. Separate administration.
* **Nitroglycerin:** Potentiated vasodilator effect, leading to hypotension and headache. Monitor blood pressure.
## Monitoring
* **Acetaminophen Overdose:** Liver function tests (ALT, AST, bilirubin, INR), renal function, glucose, electrolytes, acetaminophen levels, clinical signs of hepatotoxicity. Monitor for anaphylactoid reactions during IV infusion.
* **Mucolytic:** Respiratory status, sputum volume and consistency, signs of bronchospasm.
## Clinical Pearls
* For IV acetylcysteine in acetaminophen overdose, prompt administration is crucial for efficacy. Even if the initial acetaminophen level is below the nomogram line, treatment should be initiated if ingestion is significant and presentation is delayed.
* IV acetylcysteine is more effective and better tolerated than oral administration for acetaminophen overdose.
* When nebulizing acetylcysteine, consider co-administration with a bronchodilator to mitigate bronchospasm.
* The characteristic sulfurous odor of acetylcysteine can be unpleasant and may cause nausea; consider flavoring agents for oral or inhaled routes if needed.
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*Disclaimer: This information is intended for clinical use and does not replace professional medical judgment. Always verify current prescribing information with official drug compendia or regulatory agency sources.*
