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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is a mucolytic agent that also acts as an antidote for acetaminophen overdose by replenishing glutathione stores.
## Primary Indications
* **Acetaminophen Overdose:** Treatment to prevent or reduce liver toxicity.
* **Mucolytic:** To thin mucus in respiratory conditions such as cystic fibrosis, chronic bronchitis, and pneumonia.
## Adult Dosing
**Acetaminophen Overdose:**
* **Loading Dose:** 150 mg/kg intravenously (IV) over 1 hour.
* **Second Infusion:** 50 mg/kg IV over 16 hours.
* **Alternative (Oral):** 140 mg/kg orally (PO) as a loading dose, followed by 70 mg/kg PO every 4 hours for 17 doses.
* **Maximum dose:** Not to exceed 150 mg/kg/hr for the loading dose. The total dose for the 16-hour infusion can be very high depending on patient weight.
**Mucolytic:**
* **Inhalation:** 1-10 mL of a 20% solution or 2-20 mL of a 10% solution nebulized every 2-6 hours.
* **Direct Instillation:** 1-2 mL of a 10-20% solution into the tracheobronchial tree via a nebulizer or endotracheal tube every 1-4 hours.
## Pediatric Dosing
**Acetaminophen Overdose:**
* Dosing is the same as adults based on weight (150 mg/kg IV loading dose, then 50 mg/kg IV over 16 hours).
* For children weighing less than 40 kg, the maximum initial IV bolus should not exceed 150 mg/kg.
* Oral dosing for pediatric patients is the same as adults based on weight (140 mg/kg PO loading dose, then 70 mg/kg PO every 4 hours for 17 doses).
**Mucolytic:**
* **Inhalation:**
* **3 months to 6 years:** 1-2 mL of a 20% solution or 2-4 mL of a 10% solution nebulized every 2-6 hours.
* **7 years and older:** 1-10 mL of a 20% solution or 2-20 mL of a 10% solution nebulized every 2-6 hours.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment when used for acetaminophen overdose; however, caution is advised in severe impairment. For mucolytic use, adjustments are generally based on patient tolerance and response.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
## Adverse Effects
* **Most Common (IV for OD):** Anaphylactoid reactions (rash, pruritus, bronchospasm, angioedema, dyspnea, hypotension), nausea, vomiting.
* **Inhalation:** Bronchospasm, stomatitis, rhinorrhea, nausea.
* **Oral:** Nausea, vomiting.
## Key Drug Interactions
* No significant drug interactions are established.
## Monitoring
* **Acetaminophen Overdose:** Serum acetaminophen levels, liver function tests (AST, ALT, bilirubin, INR), and clinical signs of hepatotoxicity. Monitor for anaphylactoid reactions.
* **Mucolytic:** Patient's respiratory status, presence of bronchospasm, and sputum production.
## Clinical Pearls
* For IV administration in acetaminophen overdose, dilution of the loading dose may be necessary to reduce the risk of anaphylactoid reactions, especially in pediatric patients. Local protocols should be followed.
* Ensure adequate hydration when acetylcysteine is administered orally.
* The odor of acetylcysteine is unpleasant; this may affect patient adherence with oral or inhaled routes.
* Bronchodilators may be administered prior to or concurrently with acetylcysteine inhalation to prevent or treat bronchospasm.
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**Disclaimer:** This information is intended for clinical professionals and is not a substitute for detailed prescribing information or professional medical advice. Always consult the most current drug information and institutional protocols before making clinical decisions.
