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# Acetylcysteine
## Overview
Acetylcysteine (N-acetylcysteine, NAC) is a mucolytic agent that works by breaking disulfide bonds in mucus, reducing its viscosity. It also acts as an antidote to acetaminophen overdose by replenishing hepatic glutathione stores.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver damage.
* **Mucolytic:** To thin respiratory secretions in conditions like cystic fibrosis, chronic bronchitis, and pneumonia.
## Adult Dosing
**Acetaminophen Overdose:**
* **IV Loading Dose:** 150 mg/kg over 1 hour.
* **IV Maintenance Doses:**
* 12.5 mg/kg/hour for 4 hours.
* 6.25 mg/kg/hour for 16 hours.
* Total duration: 21 hours.
* **Oral Dosing (less preferred due to vomiting):** Typically a 72-hour regimen, starting with 140 mg/kg every 4 hours for 17 doses, followed by 70 mg/kg every 4 hours for 17 doses.
* Maximum IV dose often limited by protocol, but initial loading dose is typically 150 mg/kg.
**Mucolytic:**
* **Nebulization:** 3 mL of 10% or 20% solution every 3-4 hours as needed.
* **Oral:** 200 mg twice daily to 600 mg three times daily.
Dosing for acetaminophen overdose may vary based on local protocol and acetaminophen serum concentration timing.
## Pediatric Dosing
**Acetaminophen Overdose:**
* **IV Loading Dose:** 150 mg/kg over 1 hour.
* **IV Maintenance Doses:**
* 12.5 mg/kg/hour for 4 hours.
* 6.25 mg/kg/hour for 16 hours.
* Total duration: 21 hours.
* **Oral Dosing:** Similar to adults, but adjusted for weight.
* Maximum IV dose is typically capped at 150 mg/kg for the loading dose.
**Mucolytic:**
* **Nebulization:** 1 mL of 20% solution or 2-4 mL of 10% solution every 3-4 hours as needed.
* **Oral:** 5-10 mg/kg per dose up to twice daily, or 100-200 mg twice daily for children older than 2 years.
Specific pediatric dosing may vary based on age and weight, and local protocols.
## Dose Adjustments
* **Hepatic Impairment:** No specific dose adjustment is usually recommended for the antidote indication, as the drug is designed to protect the liver. For mucolytic use, caution may be advised, but definitive guidance is lacking.
* **Renal Impairment:** No specific dose adjustment is usually recommended.
## Contraindications
* Known hypersensitivity to acetylcysteine or any component of the formulation.
* In acute overdose, caution with bronchospasm if administered via nebulization.
## Adverse Effects
* **Anaphylactoid reactions:** Rash, pruritus, urticaria, bronchospasm, angioedema (more common with IV administration).
* **Gastrointestinal:** Nausea, vomiting, diarrhea.
* **Respiratory:** Bronchorrhea, potential for airway obstruction with excessive secretions.
* **Other:** Fever, headache, injection site reactions (with IV).
## Key Drug Interactions
* **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its efficacy in acetaminophen overdose. If both are used, separate administration by at least 1 hour.
* **Nitroglycerin:** May potentiate nitroglycerin's vasodilatory effects, leading to hypotension and headache.
## Monitoring
* **Acetaminophen Overdose:**
* Acetaminophen serum levels (peak and at least 4 hours post-ingestion).
* Liver function tests (ALT, AST, bilirubin, INR).
* Renal function and electrolytes.
* Blood glucose.
* **Mucolytic:**
* Respiratory status, sputum volume and consistency.
* Bronchospasm.
## Clinical Pearls
* IV acetylcysteine for acetaminophen overdose is most effective when started within 8-10 hours of ingestion. However, it should still be administered even if initiated later, as it may still provide benefit.
* The oral formulation has a strong sulfur odor and taste, often requiring antiemetics and flavoring agents.
* Anaphylactoid reactions are common with IV administration and can be managed with antihistamines and bronchodilators, and sometimes by slowing the infusion rate.
* Ensure adequate suctioning is available when using acetylcysteine as a mucolytic, especially in patients with compromised airway clearance.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before initiating or modifying drug therapy.*
