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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that works by decreasing the viscosity of mucus. It is also an antidote for acetaminophen overdose.
## Primary Indications
* Management of acetaminophen overdose.
* Adjunct treatment of chronic bronchitis, emphysema, and other conditions associated with excessive or thickened bronchial secretions.
## Adult Dosing
### Acetaminophen Overdose
The standard protocol involves an initial intravenous (IV) loading dose followed by maintenance doses.
* **Loading Dose:** 150 mg/kg IV over 1 hour.
* **Second Dose:** 50 mg/kg IV over the next 4 hours.
* **Third Dose:** 100 mg/kg IV over the following 16 hours.
The total daily dose should not exceed 300 mg/kg. Local protocols may vary regarding infusion rates and duration.
### Mucolytic Therapy
* **Inhalation:** 1-10 mL of a 20% solution or 2-20 mL of a 10% solution, nebulized every 3-4 hours, as needed.
* **Oral:** 200 mg orally twice daily up to 600 mg twice daily.
## Pediatric Dosing
### Acetaminophen Overdose
Dosing is the same as adults:
* **Loading Dose:** 150 mg/kg IV over 1 hour.
* **Second Dose:** 50 mg/kg IV over the next 4 hours.
* **Third Dose:** 100 mg/kg IV over the following 16 hours.
The total daily dose should not exceed 300 mg/kg.
### Mucolytic Therapy
* **Inhalation:**
* Children < 2 years: 1-2 mL of 20% solution or 2-4 mL of 10% solution, nebulized every 2-6 hours.
* Children > 2 years: 1-10 mL of 20% solution or 2-20 mL of 10% solution, nebulized every 3-4 hours, as needed.
* **Oral:** Dosing is less established and varies by indication. Consult specific pediatric guidelines.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment. However, caution is advised in severe impairment due to potential accumulation.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
## Adverse Effects
* **IV Administration:** Anaphylactoid reactions (rash, pruritus, bronchospasm, angioedema, hypotension), flushing, fever, headache, nausea, vomiting.
* **Inhalation:** Bronchospasm (especially in asthmatics), stomatitis, nausea, vomiting, rhinorrhea.
* **Oral:** Nausea, vomiting, diarrhea, rash.
## Key Drug Interactions
* **Activated Charcoal:** May bind to oral acetylcysteine, reducing its absorption. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May cause additive hypotension and headache. Monitor closely.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels at appropriate time points (e.g., 4 hours post-ingestion).
* Liver function tests (LFTs) and coagulation parameters (PT/INR).
* Clinical assessment for signs of hepatotoxicity.
* **Mucolytic Therapy:**
* Respiratory status and sputum production.
* For inhaled route, monitor for bronchospasm.
## Clinical Pearls
* For IV administration in acetaminophen overdose, the infusion bag should be prepared fresh and used within 24 hours.
* Prophylactic diphenhydramine may be considered to mitigate anaphylactoid reactions with IV acetylcysteine.
* Dilute IV acetylcysteine to an appropriate concentration (e.g., 3 mg/mL) to minimize risk of adverse reactions.
* Oral acetylcysteine has an unpleasant sulfurous odor which may be a barrier to adherence.
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**Disclaimer:** This information is intended for clinical decision-making and does not replace the need to consult the official prescribing information and current clinical guidelines. Dosing and recommendations may vary based on patient-specific factors and institutional protocols.
