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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is an mucolytic agent that decreases the viscosity of respiratory tract secretions. It also acts as an antidote for acetaminophen overdose by replenishing glutathione stores.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or treat hepatotoxicity.
* **Mucolytic:** To thin and loosen mucus in conditions such as chronic bronchitis, emphysema, and cystic fibrosis.
## Adult Dosing
**Acetaminophen Overdose:**
* **Oral Loading Dose:** 140 mg/kg.
* **Oral Maintenance Dose:** 70 mg/kg every 4 hours for 17 doses.
* **Intravenous (IV) Loading Dose:** 150 mg/kg infused over 1 hour.
* **IV Maintenance Dose:** 50 mg/kg infused over 4 hours, followed by 100 mg/kg infused over 16 hours. (Total duration 21 hours). A continuous infusion of 150 mcg/kg/min may be used after the initial bolus for IV administration in some protocols.
**Mucolytic:**
* **Inhaled:** 1 to 10 mL of a 10% or 20% solution every 2 to 6 hours as needed. May be administered alone or with a bronchodilator. Maximum dose typically not specified but guided by clinical response and tolerance.
## Pediatric Dosing
**Acetaminophen Overdose:**
* Dosing is the same as adults (140 mg/kg PO loading, 70 mg/kg PO q4h for 17 doses or IV regimens as above). Due to the large volumes required for loading doses in infants and small children, dilution may be necessary.
**Mucolytic:**
* **Inhaled:** 1 to 10 mL of a 10% or 20% solution every 2 to 6 hours as needed. May be administered alone or with a bronchodilator.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, although caution is advised in severe impairment.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active hemorrhage (for inhaled use, though this is debated and depends on risk-benefit).
## Adverse Effects
* **Inhaled:** Bronchospasm, bronchoconstriction, stomatitis, nausea, vomiting, rhinorrhea.
* **IV (Acetaminophen Overdose):** Anaphylactoid reactions (rash, pruritus, urticaria, angioedema, bronchospasm, dyspnea, hypotension), flushing, fever. Nausea and vomiting are common.
* **Oral (Acetaminophen Overdose):** Nausea, vomiting, diarrhea.
## Key Drug Interactions
* **Activated Charcoal:** May bind to oral acetylcysteine, reducing its absorption. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** Concurrent use may lead to hypotension and severe headache.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels (timing is critical for interpreting results).
* Liver function tests (AST, ALT, bilirubin, INR).
* Renal function.
* Electrolytes.
* For IV administration: Vital signs, signs of anaphylactoid reaction.
* **Mucolytic:**
* Pulmonary function.
* Sputum production.
* Signs of bronchospasm.
## Clinical Pearls
* The efficacy of acetylcysteine for acetaminophen overdose is highly dependent on timely administration. Early treatment is crucial.
* For inhaled acetylcysteine, pre-treatment with a bronchodilator may be necessary in patients prone to bronchospasm.
* Dilution of IV acetylcysteine for overdose may be necessary to manage fluid load, especially in pediatric patients. Specific dilution protocols may vary by institution.
* Anaphylactoid reactions to IV acetylcysteine are common but typically manageable with dose reduction or temporary interruption.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and clinical guidelines for complete details before making any treatment decisions.
