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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent and an antidote for acetaminophen overdose. It works by breaking disulfide bonds in mucoproteins, reducing mucus viscosity, and by replenishing glutathione stores depleted by toxic acetaminophen metabolites.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver toxicity.
* **Mucolytic Agent:** For conditions associated with thick, tenacious mucus secretions (e.g., cystic fibrosis, chronic bronchitis, pneumonia).
## Adult Dosing
### Acetaminophen Overdose:
* **Oral:** Loading dose of 140 mg/kg, followed by 70 mg/kg every 4 hours for 17 doses (total of 72 hours). Maximum dose is generally not specified for the oral route but based on body weight.
* **Intravenous (IV):** Commonly administered as a 3-bag, 72-hour protocol:
* Bag 1: 150 mg/kg in 200 mL NS, infused over 60 minutes.
* Bag 2: 50 mg/kg in 450 mL NS, infused over 16 hours.
* Bag 3: 100 mg/kg in 550 mL NS, infused over the next 16 hours.
* **Maximum IV loading dose is typically capped at 150 mg/kg.** Alternative IV protocols exist; **confirm with local protocol.**
### Mucolytic Agent:
* **Oral:** 200 mg to 400 mg twice to three times daily.
* **Inhaled:** 10% solution: 3 to 5 mL every 3 to 4 hours. 20% solution: 3 to 5 mL every 3 to 4 hours. Maximum 30 mL per day.
* **Intravenous:** Usually reserved for acetaminophen overdose. Other indications are less common and dosing is highly variable.
## Pediatric Dosing
### Acetaminophen Overdose:
* **Oral:** Same as adult: 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
* **Intravenous (IV):** Same 3-bag, 72-hour protocol as adult. **Maximum IV loading dose is typically capped at 150 mg/kg.** Alternative IV protocols exist; **confirm with local protocol.**
### Mucolytic Agent:
* **Oral:** 200 mg twice daily for children < 2 years; 200 mg two to three times daily for children 2-12 years.
* **Inhaled:** 10% or 20% solution: 1 to 3 mL every 3 to 4 hours.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment typically recommended, but caution advised.
* **Hepatic Impairment:** No specific dose adjustment typically recommended for acetaminophen overdose, as the goal is to restore glutathione; however, close monitoring is essential.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active bronchospasm (for inhaled).
## Adverse Effects
* **Most Common (Oral/IV for overdose):** Nausea, vomiting, rash, pruritus, angioedema, anaphylactoid reactions (can be severe and mimic anaphylaxis). Bronchospasm can occur, especially with rapid IV infusion.
* **Inhaled:** Bronchospasm, stomatitis, rhinorrhea, nausea, vomiting.
## Key Drug Interactions
* **Activated Charcoal:** May bind to oral acetylcysteine, reducing its absorption. If given, separate administration by at least 1 hour.
* **Nitroglycerin:** May potentiate hypotensive effects. Monitor blood pressure.
## Monitoring
* **Acetaminophen Overdose:**
* **Liver Function Tests (LFTs):** AST, ALT, bilirubin, INR (at 4, 12, 24, 48, 72 hours post-ingestion or until normalized).
* **Acetaminophen Levels:** Serial levels to assess risk and guide duration of therapy.
* **Renal Function:** BUN, creatinine.
* **Electrolytes.**
* **Clinical signs of hepatotoxicity.**
* **Mucolytic:**
* Pulmonary status, sputum viscosity.
* Bronchospasm.
## Clinical Pearls
* For acetaminophen overdose, initiating IV acetylcysteine within 8 hours of ingestion is associated with the best outcomes. However, therapy should still be initiated even if presentation is delayed, as it can still be beneficial.
* Anaphylactoid reactions to IV acetylcysteine are common and usually dose-related. They can often be managed by slowing the infusion rate.
* Oral acetylcysteine can be very unpalatable; mixing with flavored beverages may improve tolerance.
* A negative acetaminophen level does not rule out overdose if taken very recently. A nomogram should be used to assess risk.
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*Please verify current prescribing information and consult with a qualified healthcare professional before making any clinical decisions.*
