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# Acetylcysteine
## Overview
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 conditions like bronchitis, COPD, cystic fibrosis, and pneumonia.
## Adult Dosing
### Acetaminophen Overdose
* **Loading Dose:** 150 mg/kg IV over 1 hour.
* **Second Dose:** 50 mg/kg IV over 4 hours.
* **Third Dose:** 100 mg/kg IV over 16 hours.
* Maximum total dose: 150 mg/kg/hr for the first 2 hours, then 200 mg/kg/hr for the subsequent 20 hours.
* Dosing adjustments may be necessary based on serum acetaminophen levels and clinical presentation. An alternative protocol with higher initial doses exists and may be preferred in some centers. Refer to local protocol.
### Mucolytic
* **Nebulized:** 3 mL of 20% solution (600 mg) or 6 mL of 10% solution (600 mg) every 2-6 hours. Alternatively, 600 mg once daily.
* **Oral (Effervescent Tablets/Granules):** 200 mg to 600 mg twice daily.
* **Intravenous:** For specific indications like contrast-induced nephropathy prevention (dosing varies, often 600-1200 mg PO BID). IV use for mucolytic purposes is less common and dosing varies.
## Pediatric Dosing
### Acetaminophen Overdose
* Dosing is weight-based, identical to adults (150 mg/kg IV over 1 hour, then 50 mg/kg IV over 4 hours, then 100 mg/kg IV over 16 hours).
* Maximum doses should be calculated based on the child's weight.
### Mucolytic
* **Nebulized:**
* Infants and children < 1 year: 50 mg (2.5 mL of 10% solution) every 2-6 hours.
* Children 1-2 years: 100 mg (5 mL of 10% solution) every 2-6 hours.
* Children > 2 years: 200 mg (10 mL of 10% solution or 3.3 mL of 20% solution) every 2-6 hours.
* **Oral:** Dosing varies by age and indication, consult specific pediatric guidelines.
## Dose Adjustments
* No specific dose adjustment for renal or hepatic impairment is generally recommended for acetaminophen overdose protocols.
* For mucolytic use, dose adjustments are based on patient response and tolerance.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active gastrointestinal bleeding (for oral formulations).
## Adverse Effects
* **Anaphylactoid reactions:** Bronchospasm, rash, pruritus, angioedema, urticaria, hypotension. Often dose-related and can occur with IV administration.
* **Nausea and vomiting:** Common with oral and IV administration.
* **Bronchorrhea:** Increased secretions.
* **Stomatitis, rhinorrhea.**
* **Rare:** Thrombocytopenia, fever, headache.
## Key Drug Interactions
* **Activated Charcoal:** May decrease the absorption of oral acetylcysteine.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels (at specific time points).
* Liver function tests (AST, ALT, bilirubin, INR).
* Renal function (creatinine, BUN).
* Glucose (especially with IV use).
* Signs of anaphylactoid reaction.
* **Mucolytic Use:**
* Respiratory status and secretion clearance.
* Signs of bronchospasm or increased secretions.
* Tolerance of nebulized therapy.
## Clinical Pearls
* For acetaminophen overdose, initiating treatment as soon as possible is crucial, even before serum levels are available if the ingestion is significant.
* IV acetylcysteine can cause anaphylactoid reactions. Monitor patients closely during infusion. Premedication with an antihistamine may be considered.
* Oral acetylcysteine may be less effective in patients with severe liver dysfunction due to reduced absorption.
* Dilute IV acetylcysteine for infusion to reduce the risk of adverse reactions.
* Nebulized acetylcysteine has an unpleasant odor (sulfur-like) which may cause nausea or vomiting.
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*Please verify current prescribing information for detailed dosing, indications, contraindications, warnings, and adverse effects.*
