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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is an mucolytic agent and an antidote for acetaminophen overdose. It is also used off-label for various conditions.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver toxicity.
* **Mucolytic:** To thin and loosen mucus in the airways.
## Adult Dosing
### Acetaminophen Overdose
The standard protocol involves a loading dose followed by maintenance doses. A common regimen is:
* **Loading Dose:** 150 mg/kg IV, infused over 1 hour.
* **Second Dose:** 50 mg/kg IV, infused over 1 hour.
* **Subsequent Doses:** 100 mg/kg IV, infused over 16 hours (total infusion time of 21 hours).
The maximum dose in a 24-hour period for the loading dose should not exceed 150 mg/kg, and subsequent doses should be adjusted based on patient weight to avoid exceeding recommended concentrations. An oral protocol also exists.
### Mucolytic
* **Nebulized:** 20% solution: 1-10 mL every 2-6 hours. 10% solution: 5-20 mL every 2-6 hours.
* **Oral (less common for mucolytic):** 600 mg orally once to three times daily.
## Pediatric Dosing
### Acetaminophen Overdose
Dosing is weight-based, similar to adults.
* **Loading Dose:** 150 mg/kg IV, infused over 1 hour.
* **Second Dose:** 50 mg/kg IV, infused over 1 hour.
* **Subsequent Doses:** 100 mg/kg IV, infused over 16 hours.
The total infusion time is typically 21 hours. Maximum doses should be calculated based on weight to avoid exceeding recommended concentrations. Oral dosing for children is also available and typically 140 mg/kg loading dose followed by 70 mg/kg every 4 hours for 17 doses.
### Mucolytic
* **Nebulized:**
* **Infants and young children:** 1-3 mL of 20% solution or 3-5 mL of 10% solution every 2-6 hours.
* **Older children:** 3-5 mL of 20% solution or 5-10 mL of 10% solution every 2-6 hours.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is universally recommended, but caution may be advised.
* **Hepatic Impairment:** No specific dose adjustment is universally recommended, but caution may be advised.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
## Adverse Effects
* **Anaphylactoid reactions:** Rash, pruritus, bronchospasm, angioedema, dyspnea, hypotension (more common with IV administration).
* **Nausea and vomiting:** Especially with oral administration.
* **Stomatitis:** With nebulized use.
* **Rhinorrhea:** With nebulized use.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its absorption. Administer oral NAC at least 1 hour after activated charcoal.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension and headache. Monitor blood pressure.
## Monitoring
* **Acetaminophen Overdose:** Liver function tests (AST, ALT, bilirubin, INR) at baseline and periodically (e.g., 24-48 hours post-ingestion). Acetaminophen levels to guide duration of therapy. Clinical signs of liver injury.
* **Mucolytic:** Respiratory status, frequency and character of sputum, patient's subjective improvement.
## Clinical Pearls
* For IV administration in acetaminophen overdose, it is crucial to adhere to the protocol for infusion rates to minimize the risk of anaphylactoid reactions. Dilution may be necessary to achieve appropriate infusion rates and concentrations.
* The smell of acetylcysteine is characteristically sulfurous ("rotten eggs"); this is normal.
* When used as a mucolytic, adequate hydration is important to help thin secretions.
* Consider alternative administration routes if gastrointestinal intolerance occurs with oral NAC.
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**Disclaimer:** This information is intended for clinical professionals and does not replace the need to consult the most current official prescribing information, institutional protocols, or a pharmacist for specific patient care decisions. Always verify drug information before administration.
