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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is an antidote for acetaminophen overdose and a mucolytic agent.
## Primary Indications
* Acetaminophen overdose
* Mucolytic for conditions with thick mucus secretions (e.g., cystic fibrosis, chronic bronchitis, pneumonia)
## Adult Dosing
**Acetaminophen Overdose:**
The intravenous (IV) protocol is preferred in many centers due to faster attainment of therapeutic levels and reduced risk of anaphylactoid reactions compared to oral.
* **IV Protocol (e.g., NAC ATOM protocol):**
* **Loading Dose:** 150 mg/kg IV over 60 minutes.
* **Second Infusion:** 50 mg/kg IV over 4 hours.
* **Third Infusion:** 100 mg/kg IV over 16 hours.
* **Maximum Dose:** Maximum bolus dose of 150 mg/kg should not exceed 15g. Total dose over 21 hours typically 300 mg/kg.
* **Oral Protocol:**
* **Loading Dose:** 140 mg/kg PO.
* **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses (total of 18 doses).
* **Maximum Dose:** Maximum single oral dose is typically 2000 mg.
**Mucolytic:**
* **Nebulized:** 3-10 mL of 20% solution or 6-10 mL of 10% solution every 2-6 hours.
* **Oral:** 200 mg twice daily to 600 mg three times daily.
## Pediatric Dosing
**Acetaminophen Overdose:**
Dosing is weight-based, following the same IV or oral protocols as adults.
* **IV Protocol:** Same as adult, with careful attention to total fluid volume in neonates and infants.
* **Oral Protocol:** Same as adult, with maximum single oral dose typically limited to 2000 mg or 100 mg/kg, whichever is less.
**Mucolytic:**
* **Nebulized:**
* Infants and children < 1 year: 1-2 mL of 20% solution every 2-6 hours.
* Children > 1 year: 3-5 mL of 20% solution or 6-10 mL of 10% solution every 2-6 hours.
* **Oral:** Pediatric dosing varies; typically 50-150 mg 2-3 times daily. Consult specific pediatric guidelines.
## Dose Adjustments
* **Hepatic Impairment:** No specific dose adjustment is typically required for acetaminophen overdose treatment. For mucolytic use, caution may be advised, though evidence is limited.
* **Renal Impairment:** No specific dose adjustment is typically required.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Acute bronchospasm (for nebulized use).
## Adverse Effects
* **Anaphylactoid Reactions (IV):** Rash, urticaria, angioedema, bronchospasm, hypotension. Typically occur with initial loading dose.
* **Gastrointestinal:** Nausea, vomiting, diarrhea (more common with oral administration).
* **Respiratory:** Bronchospasm, rhinorrhea, feeling of chest tightness (nebulized).
* **Other:** Fever, headache.
## Key Drug Interactions
* **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing absorption. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** Concomitant use may potentiate hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels (serial measurements).
* Liver function tests (AST, ALT, bilirubin, PT/INR).
* Renal function (BUN, creatinine).
* Glucose.
* Electrolytes.
* Signs of anaphylactoid reaction (vital signs, respiratory status).
* **Mucolytic Use:**
* Respiratory status, secretion clearance, signs of bronchospasm.
## Clinical Pearls
* The smell of acetylcysteine is often described as "rotten eggs" and can be unpleasant, contributing to nausea and vomiting, particularly with oral administration.
* For IV administration, ensure adequate hydration to minimize the risk of anaphylactoid reactions. Antihistamines may be considered as premedication.
* Protocols for IV acetylcysteine administration vary; follow institutional guidelines.
* For acetaminophen overdose, treatment should be initiated empirically if there is any doubt about the timing of ingestion or if serum acetaminophen levels are in the potentially toxic range.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and institutional protocols before administering any medication.
