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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is a mucolytic agent that breaks disulfide bonds in mucus, decreasing its viscosity. It is also an antidote for acetaminophen overdose.
## Primary Indications
* Mucolytic for respiratory conditions (e.g., COPD, cystic fibrosis, pneumonia)
* Antidote for acetaminophen overdose
## Adult Dosing
* **Mucolytic:** 600 mg inhaled once to three times daily. Higher doses may be used in specific protocols.
* **Acetaminophen Overdose:**
* **Oral:** Loading dose of 140 mg/kg, followed by 70 mg/kg every 4 hours for 17 doses (total of 18 doses).
* **Intravenous (IV):** Typically a 3-bag, 21-hour infusion protocol:
* Bag 1: 150 mg/kg IV over 60 minutes.
* Bag 2: 50 mg/kg IV over the next 60 minutes (max infusion rate of 12.5 mg/kg/hr).
* Bag 3: 100 mg/kg IV over the final 16 hours (max infusion rate of 6.25 mg/kg/hr).
* *Note: IV protocols can vary; consult local institutional guidelines.*
## Pediatric Dosing
* **Mucolytic:** 600 mg inhaled once to three times daily. Dosing may be adjusted based on patient size and ability to inhale effectively. Nebulized doses typically range from 200 mg to 600 mg per treatment.
* **Acetaminophen Overdose (Oral):** Same as adult dosing: 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
* **Acetaminophen Overdose (IV):** Same as adult IV protocol, adjusted for weight.
## Dose Adjustments
No specific dose adjustments are routinely required for hepatic or renal impairment, but caution may be warranted in severe disease.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active bronchospasm (for inhaled form).
## Adverse Effects
* **Inhaled:** Bronchospasm, bronchoconstriction, stomatitis, rhinorrhea, nausea, vomiting.
* **IV (Acetaminophen Overdose):** Anaphylactoid reactions (rash, urticaria, pruritus, bronchospasm, angioedema, dyspnea), flushing, hypotension, tachycardia. Rapid infusion can increase the risk of these reactions.
## Key Drug Interactions
* **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its efficacy for acetaminophen overdose. Separate administration by at least 1 hour.
* **Nitroglycerin:** May potentiate the vasodilator effects of nitroglycerin. Monitor for hypotension.
## Monitoring
* **Mucolytic:** Monitor respiratory status, pulmonary function, and effectiveness in airway clearance. Monitor for bronchospasm.
* **Acetaminophen Overdose:**
* Monitor acetaminophen levels, ALT/AST, INR, creatinine, and glucose.
* Monitor for signs and symptoms of hepatotoxicity.
* Monitor vital signs and for signs of anaphylactoid reactions during IV infusion.
## Clinical Pearls
* For inhaled use, acetylcysteine has a characteristic sulfurous odor, which may be unpleasant for some patients.
* When used for acetaminophen overdose, prompt administration is crucial for efficacy. The antidote is most effective when given within 8-10 hours of ingestion.
* Pretreatment with a bronchodilator may be considered in patients with reactive airway disease receiving inhaled acetylcysteine.
* Be prepared to manage anaphylactoid reactions if administering IV acetylcysteine.
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*This information is intended for clinical use and is not a substitute for professional medical advice. Always consult current prescribing information and institutional protocols.*
