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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is a mucolytic agent and an antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen Overdose:** Treatment of overdose of acetaminophen.
* **Mucolytic Agent:** To help thin mucus in respiratory conditions such as bronchitis, emphysema, and cystic fibrosis.
## Adult Dosing
### Acetaminophen Overdose (Oral or Intravenous)
* **Loading Dose:** 150 mg/kg administered intravenously over 60 minutes.
* **Second Dose:** 50 mg/kg administered intravenously over the next 60 minutes.
* **Third Dose:** 100 mg/kg administered intravenously over 16 hours.
* Total duration: 21 hours.
* **Oral Alternative:** Follows a similar protocol, with doses taken orally or via nasogastric tube. A common oral loading dose is 140 mg/kg, followed by 70 mg/kg every 4 hours for 17 doses.
### Mucolytic Agent (Inhaled)
* **Standard Dose:** 3 mL to 5 mL of a 20% solution or 6 mL to 10 mL of a 10% solution administered via nebulizer every 3 to 4 hours.
* **Alternative:** May be administered every 2 to 6 hours as needed.
## Pediatric Dosing
### Acetaminophen Overdose (Oral or Intravenous)
* Dosing is the same as for adults, based on weight (150 mg/kg IV loading dose, etc.).
* Care must be taken with IV administration in neonates and infants due to fluid volume.
### Mucolytic Agent (Inhaled)
* **Standard Dose:** 1 mL to 2 mL of a 20% solution or 2 mL to 4 mL of a 10% solution administered via nebulizer every 3 to 4 hours.
## Dose Adjustments
* No dose adjustment is generally required for renal or hepatic impairment for the antidote indication.
* For mucolytic use, dose may be adjusted based on patient response and tolerance.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active hemorrhage (for mucolytic use, caution advised).
## Adverse Effects
* **Common (Intravenous for overdose):** Anaphylactoid reactions (rash, pruritus, urticaria, bronchospasm, angioedema, dyspnea), nausea, vomiting. Rapid infusion can increase the risk of anaphylactoid reactions.
* **Common (Inhaled):** Bronchospasm, rhinorrhea, nausea, vomiting, stomatitis.
* **Less Common:** Fever, headache, tinnitus.
## Key Drug Interactions
* **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its effectiveness. Administer acetylcysteine at least 1 hour after activated charcoal if possible.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels.
* Liver function tests (AST, ALT, bilirubin, INR).
* Clinical signs of hepatotoxicity.
* Signs of anaphylactoid reaction.
* **Mucolytic Agent:**
* Respiratory status, sputum production.
* Bronchospasm.
## Clinical Pearls
* For acetaminophen overdose, treatment should be initiated as soon as possible, ideally within 8 hours of ingestion, as efficacy decreases significantly after this time.
* IV acetylcysteine can cause anaphylactoid reactions; premedication with an antihistamine and/or bronchodilator may be considered, especially in patients with a history of asthma.
* Dilute IV acetylcysteine before administration to reduce infusion-related reactions and improve patient tolerance. Follow institutional guidelines for dilution.
* N-acetylcysteine is also being investigated for various other off-label uses, but evidence is often limited.
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*Disclaimer: This information is intended for clinical decision-making support and does not replace comprehensive drug information resources or professional judgment. Always consult the official prescribing information and institutional protocols before administering any medication.*
