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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that loosens mucus. It is also an antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen overdose:** To prevent or reduce liver toxicity.
* **Mucolytic:** To thin and loosen mucus in respiratory conditions like cystic fibrosis, COPD, and pneumonia.
## Adult Dosing
### Acetaminophen Overdose
* **Oral:** Loading dose of 140 mg/kg, followed by 70 mg/kg every 4 hours for 17 doses.
* **Intravenous (IV):** Protocol varies. Common regimens include:
* **Standard 21-hour infusion:** 150 mg/kg IV over 60 minutes, then 12.5 mg/kg/hour for 4 hours, then 6.25 mg/kg/hour for 16 hours.
* **Alternative 48-hour infusion (for anticipated anaphylactoid reactions or if IV access is delayed):** 150 mg/kg IV over 15 minutes, then 12.5 mg/kg/hour for 4 hours, then 6.25 mg/kg/hour for 44.25 hours.
* *Specific IV dosing protocols may vary by institution and patient factors (e.g., acetaminophen levels).*
### Mucolytic
* **Inhalation:** 3 mL to 5 mL of a 10% or 20% solution nebulized every 3 to 4 hours. Higher doses may be used in specific protocols.
* **Oral (less common):** 200 mg to 400 mg two to three times daily.
## Pediatric Dosing
### Acetaminophen Overdose
* **Oral:** Dosing is weight-based, identical to adults (140 mg/kg loading, 70 mg/kg every 4 hours for 17 doses).
* **Intravenous (IV):** Similar infusion protocols as adults, adjusted for weight.
* **Standard 21-hour infusion:** 150 mg/kg IV over 60 minutes, then 12.5 mg/kg/hour for 4 hours, then 6.25 mg/kg/hour for 16 hours.
* *Specific IV dosing protocols may vary by institution.*
### Mucolytic
* **Inhalation:** 1 mL to 5 mL of a 10% or 20% solution nebulized every 3 to 4 hours.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment for the mucolytic indication. For acetaminophen overdose, severe hepatic impairment may warrant closer monitoring and consideration of alternative antidote protocols, though standard dosing is often still used.
## Contraindications
* Hypersensitivity to acetylcysteine.
## Adverse Effects
* **Inhalation:** Bronchospasm (especially in asthmatics), stomatitis, rhinorrhea, nausea, vomiting. Anaphylactoid reactions can occur with IV administration.
* **Oral:** Nausea, vomiting, diarrhea.
* **Intravenous:** Anaphylactoid reactions (most common and serious), rash, urticaria, bronchospasm, facial flushing, tachycardia, hypotension.
## Key Drug Interactions
None generally considered clinically significant for the mucolytic indication.
## Monitoring
* **Acetaminophen overdose:**
* Serum acetaminophen levels (at specific time points post-ingestion).
* Liver function tests (AST, ALT, bilirubin, INR).
* Renal function.
* Electrolytes.
* Glucose.
* **Mucolytic:**
* Pulmonary function.
* Signs of bronchospasm.
## Clinical Pearls
* For acetaminophen overdose, initiate acetylcysteine immediately if overdose is suspected, even before acetaminophen levels are available, as delaying treatment can lead to irreversible liver damage.
* IV acetylcysteine can cause anaphylactoid reactions. Pretreatment with an antihistamine may be considered, and patients should be closely monitored for signs of hypersensitivity.
* When nebulizing, use a bronchodilator prior to acetylcysteine if the patient has reactive airway disease to minimize bronchospasm.
* The odor of acetylcysteine is unpleasant; this can be a challenge for adherence, especially with oral formulations.
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**Disclaimer:** This information is intended for educational purposes only and does not substitute for professional medical advice. Always consult the current prescribing information and your healthcare provider for accurate and up-to-date guidance on drug use.
