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# Acetylcysteine
## Overview
Acetylcysteine (N-acetylcysteine, NAC) is a mucolytic agent and an antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver toxicity.
* **Mucolytic:** To thin and loosen mucus in airway diseases such as COPD, cystic fibrosis, and pneumonia.
## Adult Dosing
* **Acetaminophen Overdose:**
* **Intravenous (IV):** A loading dose of 150 mg/kg over 1 hour, followed by 50 mg/kg over 4 hours, and then 100 mg/kg over the next 16 hours. A total of 300 mg/kg over 21 hours. Maximum infusion rates vary by protocol but typically do not exceed 12.5 g over 21 hours.
* **Oral:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
* **Mucolytic:**
* **Inhaled:** 3 mL to 5 mL of a 10% or 20% solution nebulized every 4 to 12 hours.
* **Oral:** 200 mg to 600 mg two to three times daily.
## Pediatric Dosing
* **Acetaminophen Overdose:**
* **Intravenous (IV):** Same protocol as adults: 150 mg/kg over 1 hour, followed by 50 mg/kg over 4 hours, and then 100 mg/kg over the next 16 hours. Maximum cumulative dose for children is often lower than adults; refer to local protocols.
* **Oral:** Same protocol as adults: 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
* **Mucolytic:**
* **Inhaled:** 1 mL to 2 mL of a 10% or 20% solution nebulized every 4 to 12 hours.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, but caution is advised in severe cases, particularly for IV administration where fluid volume might be a concern.
## Contraindications
* Hypersensitivity to acetylcysteine.
* Active hemorrhage (for inhaled use).
## Adverse Effects
* **Intravenous:** Anaphylactoid reactions (rash, urticaria, pruritus, bronchospasm, angioedema, dyspnea, hypotension, tachycardia) are common and can be severe. Nausea and vomiting are also frequent.
* **Inhaled:** Bronchospasm, stomatitis, rhinorrhea, nausea.
* **Oral:** Nausea, vomiting, diarrhea, rash.
## Key Drug Interactions
* **Activated Charcoal:** May reduce the absorption of oral acetylcysteine. If used concurrently for overdose, administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May potentiate hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:** Liver function tests (AST, ALT, bilirubin, INR), acetaminophen levels, serum creatinine, glucose. Monitor for signs of anaphylactoid reaction during IV infusion.
* **Mucolytic:** Respiratory status, sputum production, and thickness.
## Clinical Pearls
* For IV administration in acetaminophen overdose, a 21-hour protocol is standard. Treatment should be initiated as soon as possible after ingestion.
* Anaphylactoid reactions to IV acetylcysteine are common but usually not life-threatening. Slowing the infusion rate may help manage symptoms. Antihistamines can be used prophylactically or for treatment.
* Inhaled acetylcysteine can cause bronchospasm, especially in patients with asthma or hyperreactive airways. Co-administration of a bronchodilator is often recommended.
* The odor of acetylcysteine is strong (sulfur-like) and can be unpleasant.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making therapeutic decisions.*
