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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucus, decreasing its viscosity. It is also an antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen overdose:** To prevent or reduce liver toxicity.
* **Mucolytic:** To thin mucus in respiratory conditions such as cystic fibrosis, bronchitis, and pneumonia.
## Adult Dosing
* **Acetaminophen overdose:**
* **Loading Dose:** 150 mg/kg intravenously (IV) over 1 hour.
* **Second Dose:** 50 mg/kg IV over 4 hours.
* **Subsequent Doses:** 100 mg/kg IV over 16 hours.
* A continuous infusion of 100 mg/kg/hr for up to 72 hours may be used in severe cases or if hepatic injury progresses.
* Maximum total dose is not well-defined but can exceed 300 mg/kg if needed.
* Oral dosing is an alternative, typically 140 mg/kg loading dose followed by 70 mg/kg every 4 hours for 17 doses.
* **Mucolytic:**
* **Inhaled:** 3 mL to 5 mL of a 10% or 20% solution nebulized every 2-6 hours, or 1 mL of a 10% solution nebulized every 2-6 hours for pediatric patients. Alternatively, 20% solution can be diluted to 5-10% with sterile water or saline.
* **Oral (Effervescent Tablets):** 200 mg to 400 mg (1 to 2 tablets) every 4 to 12 hours.
* **Intravenous (for airway protection during bronchoscopy):** 150 mg/kg IV infused over 15 minutes followed by 30 mg/kg/hr for 4 hours, then 15 mg/kg/hr for up to 48 hours.
* **Intranasal:** 1% to 2% solution instilled intranasally.
## Pediatric Dosing
* **Acetaminophen overdose:** Dosing is weight-based as described in Adult Dosing.
* **Mucolytic:**
* **Inhaled:** 3 mL of a 10% solution nebulized every 2-6 hours or 1 mL of a 10% solution nebulized every 2-6 hours. Some protocols suggest higher doses for certain conditions.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are typically recommended, but caution is advised.
* **Hepatic Impairment:** Acetaminophen overdose protocol generally continues regardless of hepatic function, as it is used to prevent further injury.
## Contraindications
* Known hypersensitivity to acetylcysteine or any component of the formulation.
* Certain preparations may contain sulfite, which can cause allergic-type reactions, including anaphylaxis, in susceptible individuals.
## Adverse Effects
* **Inhaled:** Bronchospasm, bronchoconstriction, rhinorrhea, stomatitis, nausea, vomiting.
* **Intravenous (Acetaminophen Overdose):** Anaphylactoid reactions (ranging from rash, pruritus, to bronchospasm, angioedema, and anaphylaxis), flushing, urticaria, hypotension, tachycardia.
* **Oral:** Nausea, vomiting, diarrhea, rash.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb acetylcysteine, reducing its effectiveness in acetaminophen overdose. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May potentiate hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:** Serum acetaminophen levels, liver function tests (AST, ALT, bilirubin, INR), renal function, and clinical status.
* **Mucolytic:** Respiratory status, sputum production and viscosity.
## Clinical Pearls
* For IV administration in acetaminophen overdose, anaphylactoid reactions are common and can be severe. Pretreatment with an antihistamine may be considered.
* The smell of acetylcysteine is characteristically sulfurous and may be unpleasant for patients.
* For inhaled use, bronchospasm can occur. Administering a bronchodilator prior to acetylcysteine may be beneficial.
* The efficacy of acetylcysteine for acetaminophen overdose is highest when initiated within 8-10 hours of ingestion.
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*Disclaimer: This information is intended for healthcare professionals. Always consult current prescribing information and local protocols for definitive guidance. Dosing may vary based on patient-specific factors and clinical context.*
