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# Acetylcysteine
## Overview
Acetylcysteine is an antidote for acetaminophen overdose and a mucolytic agent.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver toxicity following an acute acetaminophen overdose.
* **Mucolytic Agent:** To thin and loosen mucus secretions in respiratory conditions such as chronic bronchitis, emphysema, cystic fibrosis, and atelectasis.
## Adult Dosing
**Acetaminophen Overdose:**
* **Intravenous (IV) Administration:**
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Dose:** 50 mg/kg IV infused over 16 hours.
* **Third Dose:** 100 mg/kg IV infused over 16 hours.
* *Note:* Protocols may vary; a common alternative is a continuous infusion of 150 mg/kg/hr for 4 hours, followed by 12.5 mg/kg/hr for 16 hours. Specific IV protocols depend on local guidelines and the time since acetaminophen ingestion.
* **Oral (PO) Administration:**
* **Loading Dose:** 140 mg/kg PO.
* **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses (total of 18 doses).
* *Note:* Oral administration may be less effective and is often associated with increased nausea and vomiting, particularly at higher doses. Antiemetics may be required.
**Mucolytic Agent:**
* **Nebulized:** 3 mL of a 10% or 20% solution (300-600 mg) every 3-4 hours as needed. Higher doses or more frequent administration may be used in severe cases, particularly in cystic fibrosis.
* **Oral:** 200 mg twice daily or 600 mg once daily for chronic bronchitis.
## Pediatric Dosing
**Acetaminophen Overdose:**
* **Intravenous (IV) Administration:** Dosing is the same as adult: 150 mg/kg IV over 1 hour, then 50 mg/kg IV over 16 hours, then 100 mg/kg IV over 16 hours. Maximum dose is typically 150 mg/kg/day.
* **Oral (PO) Administration:** Dosing is the same as adult: 140 mg/kg PO loading dose, followed by 70 mg/kg PO every 4 hours for 17 doses.
**Mucolytic Agent (Nebulized):**
* **3 months to 6 years:** 1 mL of 20% solution (200 mg) or 2 mL of 10% solution (200 mg) every 2-6 hours.
* **Over 6 years:** 3 mL of 10% or 20% solution (300-600 mg) every 3-4 hours.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment in the context of acetaminophen overdose. For mucolytic use, adjust based on patient response and tolerance.
## Contraindications
* Hypersensitivity to acetylcysteine or other components.
* **Oral use:** Active peptic ulcer.
## Adverse Effects
* **Intravenous:** Anaphylactoid reactions (rash, pruritus, urticaria, bronchospasm, angioedema, hypotension), flushing, fever.
* **Nebulized:** Bronchospasm (especially in asthmatics), rhinorrhea, nausea, vomiting, stomatitis.
* **Oral:** Nausea, vomiting, diarrhea, rash, fever.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its absorption. Administer oral acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May potentiate hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:**
* **Liver Function Tests (LFTs):** AST, ALT, bilirubin, prothrombin time.
* **Renal Function:** BUN, creatinine.
* **Electrolytes.**
* **Acetaminophen levels:** To assess the extent of exposure and guide duration of treatment.
* **Mucolytic Use:** Respiratory status, sputum viscosity, patient tolerance.
## Clinical Pearls
* For IV acetylcysteine in acetaminophen overdose, ensure adequate hydration and monitor for anaphylactoid reactions. Have epinephrine, antihistamines, and bronchodilators readily available.
* Nebulized acetylcysteine can induce bronchospasm. Consider co-administration with a bronchodilator (e.g., albuterol).
* The smell of acetylcysteine is often described as unpleasant (rotten eggs).
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*This information is intended for healthcare professionals and is a summary of essential points. It is not exhaustive and does not replace a thorough review of the full prescribing information. Always consult current product labeling and institutional protocols for complete and up-to-date guidance.*
