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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that decreases the viscosity of respiratory secretions and an antidote for acetaminophen overdose by replenishing hepatic glutathione stores.
## Primary Indications
* **Acetaminophen overdose:** To prevent or reduce liver toxicity.
* **Thick mucus in respiratory conditions:** Such as cystic fibrosis, chronic bronchitis, and pneumonia.
## Adult Dosing
### Acetaminophen Overdose
* **Loading Dose:** 150 mg/kg IV over 1 hour.
* **Second Dose:** 50 mg/kg IV over the next 1 hour.
* **Third Dose:** 100 mg/kg IV over the next 16 hours.
* Total daily dose should not exceed 300 mg/kg.
* **Oral alternative:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
* The maximum oral dose is 17 doses.
### Mucolytic
* **Inhaled:** 10% solution: 3-5 mL via nebulizer every 6-8 hours. 20% solution: 3-5 mL via nebulizer every 6-8 hours.
* **Oral:** 200 mg to 400 mg (or 600 mg) two to three times daily.
## Pediatric Dosing
### Acetaminophen Overdose
* Dosing is the same as adults (150 mg/kg IV loading, 50 mg/kg IV second dose, 100 mg/kg IV over 16 hours).
* Oral dosing is the same as adults (140 mg/kg loading, 70 mg/kg every 4 hours for 17 doses).
### Mucolytic
* **Inhaled:**
* **< 1 year:** 1-2 mL of 10% solution every 2-6 hours.
* **1-2 years:** 2-3 mL of 10% solution every 2-6 hours.
* **> 2 years:** 3-5 mL of 10% solution every 2-6 hours.
* **Oral:** 10 mg/kg to 20 mg/kg per dose, up to 600 mg/day, in 2-3 divided doses.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, but caution is advised in severe impairment.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
## Adverse Effects
* **IV:** Anaphylactoid reactions (rash, pruritus, bronchospasm, angioedema), hypotension, tachycardia, nausea, vomiting.
* **Inhaled:** Bronchospasm, stomatitis, rhinorrhea, nausea.
* **Oral:** Nausea, vomiting, diarrhea, rash.
## Key Drug Interactions
* **Activated charcoal:** Can bind to oral acetylcysteine, reducing its absorption. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** Potentiates hypotensive effects. Monitor blood pressure closely.
## Monitoring
* **Acetaminophen overdose:**
* Serum acetaminophen levels.
* Liver function tests (AST, ALT, bilirubin, INR).
* Prothrombin time.
* Renal function.
* **Mucolytic:**
* Respiratory status, sputum thickness and ease of expectoration.
* Bronchospasm.
## Clinical Pearls
* For IV administration, acetylcysteine can be diluted in normal saline, dextrose 5% in water, or lactated Ringer's solution.
* Monitor closely for anaphylactoid reactions during IV infusion, especially during the loading dose. Have emergency equipment readily available.
* Bronchodilators may be administered prior to inhaled acetylcysteine to prevent bronchospasm.
* The smell of sulfur is characteristic and expected.
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*Please consult the most current prescribing information and institutional protocols for definitive guidance.*
