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# Acetylcysteine
## Overview
Acetylcysteine (N-acetylcysteine, NAC) is a mucolytic agent and an antidote for acetaminophen overdose. It is available in oral and intravenous formulations.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver damage following an acetaminophen overdose.
* **Mucolytic:** To thin mucus in respiratory conditions such as bronchitis, cystic fibrosis, and COPD.
## Adult Dosing
* **Acetaminophen Overdose:**
* **Oral:** Loading dose of 140 mg/kg, followed by 70 mg/kg every 4 hours for 17 doses. Maximum dose of 140 mg/kg per dose for loading and subsequent doses if needed.
* **Intravenous:** A common protocol involves a loading dose of 150 mg/kg infused over 60 minutes, followed by 50 mg/kg infused over 4 hours, then 100 mg/kg infused over 16 hours. Dosing adjustments may be necessary based on acetaminophen levels and time since ingestion. Specific IV protocols can vary; consult local guidelines.
* **Mucolytic (Oral or Nebulized):**
* **Oral:** Typically 200 mg to 400 mg twice or three times daily.
* **Nebulized:** 1 mL to 10 mL of a 10% solution or 2 mL to 10 mL of a 20% solution every 2 to 6 hours as needed. The concentration and frequency may vary based on patient tolerance and clinical response.
## Pediatric Dosing
* **Acetaminophen Overdose:**
* **Oral:** Same as adult dosing: 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
* **Intravenous:** Dosing is weight-based and follows similar tiered infusion rates as adults. Specific IV protocols vary and should be followed based on local guidelines.
* **Mucolytic (Nebulized):** Dosing is weight-based and concentration-dependent. Common starting doses for infants and children range from 200 mg to 600 mg per day, divided into multiple nebulizations. Consult pediatric guidelines for specific recommendations.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended for mild to moderate renal impairment. Use with caution in severe renal impairment.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended. However, patients with hepatic impairment are at higher risk for acetaminophen toxicity.
## Contraindications
* Hypersensitivity to acetylcysteine.
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, stomatitis, rash, pruritus, rhinorrhea, bronchospasm (especially with nebulized formulation).
* **Serious (IV for acetaminophen overdose):** Anaphylactoid reactions (hypotension, bronchospasm, angioedema, urticaria), which can be severe and life-threatening.
## Key Drug Interactions
* **Activated Charcoal:** May reduce the absorption of oral acetylcysteine. If co-administered, consider spacing doses or administering acetylcysteine first.
* **Nitroglycerin:** Concurrent use may potentiate the hypotensive effect of nitroglycerin.
## Monitoring
* **Acetaminophen Overdose:** Serial monitoring of serum acetaminophen levels, liver function tests (ALT, AST, bilirubin, prothrombin time), and renal function. Clinical signs of liver toxicity.
* **Mucolytic:** Monitor for effectiveness (improved airway clearance) and adverse effects (bronchospasm, respiratory distress).
## Clinical Pearls
* The oral antidote protocol for acetaminophen overdose is effective even if initiated >24 hours after ingestion, especially if liver injury is present.
* Anaphylactoid reactions are common with IV acetylcysteine but are usually manageable with dose modification or temporary interruption.
* A strong, unpleasant sulfurous odor is characteristic of acetylcysteine and may contribute to nausea and vomiting. Administering it with flavored beverages or juices can improve palatability.
* Nebulized acetylcysteine can thicken bronchial secretions in some patients, potentially causing airway obstruction. Monitor respiratory status closely.
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*Please verify current prescribing information and consult with a healthcare professional for personalized medical advice.*
