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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is a mucolytic agent and an antidote for acetaminophen overdose. It works by breaking disulfide bonds in mucus, reducing its viscosity, and by replenishing glutathione stores depleted by acetaminophen toxicity.
## Primary Indications
* **Acetaminophen Overdose:** Antidote.
* **Mucolytic Agent:** For conditions with thick, tenacious mucus (e.g., chronic bronchitis, cystic fibrosis, pneumonia).
## Adult Dosing
### Acetaminophen Overdose (Oral or IV)
The optimal protocol can vary slightly by institution. A common protocol involves a loading dose followed by maintenance doses.
* **Oral:**
* Loading dose: 140 mg/kg (maximum 14 g) as a single dose.
* Maintenance: 70 mg/kg (maximum 7 g) every 4 hours for 17 doses.
* **Intravenous (IV):**
* Loading dose: 150 mg/kg over 1 hour.
* Second dose: 50 mg/kg over 4 hours.
* Third dose: 100 mg/kg over 16 hours.
* *Note: IV administration can be associated with anaphylactoid reactions, requiring careful monitoring and potential premedication.*
### Mucolytic Agent
* **Nebulized:** 3 mL of a 10% or 20% solution (300-600 mg) every 2-6 hours. Higher doses may be used in specific conditions like cystic fibrosis.
* **Oral (less common for mucolytic):** 200 mg twice daily to three times daily.
## Pediatric Dosing
### Acetaminophen Overdose (Oral or IV)
Dosing is weight-based and follows similar patterns to adults, adjusted for pediatric weights.
* **Oral:**
* Loading dose: 140 mg/kg (maximum 14 g).
* Maintenance: 70 mg/kg (maximum 7 g) every 4 hours for 17 doses.
* **Intravenous (IV):**
* Loading dose: 150 mg/kg over 1 hour.
* Second dose: 50 mg/kg over 4 hours.
* Third dose: 100 mg/kg over 16 hours.
### Mucolytic Agent
* **Nebulized:** 10% solution: 1-2 mL (100-200 mg) every 2-6 hours. 20% solution: 1 mL (200 mg) every 2-6 hours. Dosing is often guided by patient tolerance and response.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended for standard dosing, but caution is advised.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended for standard dosing, but caution is advised, especially in acetaminophen overdose.
## Contraindications
* Known hypersensitivity to acetylcysteine.
* Asthma (relative contraindication for nebulized use due to potential bronchospasm; use with caution and bronchodilator pre-treatment if necessary).
## Adverse Effects
* **Anaphylactoid Reactions (especially with IV):** Rash, urticaria, pruritus, bronchospasm, dyspnea, angioedema, hypotension.
* **Nebulized:** Bronchospasm, stomatitis, nausea, vomiting, rhinorrhea.
* **Oral:** Nausea, vomiting, diarrhea, abdominal pain.
## Key Drug Interactions
* **Activated Charcoal:** May bind to oral acetylcysteine, reducing its absorption. Administer charcoal at least 1 hour apart from oral acetylcysteine.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, potentially leading to hypotension and headache.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels (serial measurements).
* Liver function tests (LFTs).
* Prothrombin time (PT)/International Normalized Ratio (INR).
* Renal function.
* Clinical signs of acetaminophen toxicity (e.g., encephalopathy, coagulopathy).
* Monitor for anaphylactoid reactions during IV infusion.
* **Mucolytic Use:**
* Respiratory status, effectiveness in clearing secretions.
* Monitor for bronchospasm.
## Clinical Pearls
* For acetaminophen overdose, treatment initiation is critical. The nomogram is a guide, but any suspected overdose should be treated promptly, especially if timing is uncertain.
* Oral acetylcysteine has an unpleasant sulfurous odor and taste; dilution with juice or carbonated beverages can improve palatability.
* IV acetylcysteine may require premedication with an antihistamine to reduce the incidence of anaphylactoid reactions.
* If bronchospasm occurs with nebulized acetylcysteine, discontinue the infusion and consider co-administration of a bronchodilator.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before administering any medication.*
