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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is a mucolytic agent and an antidote for acetaminophen overdose. It works by breaking disulfide bonds in mucoproteins, reducing mucus viscosity, and by replenishing glutathione stores depleted during acetaminophen toxicity.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver damage.
* **Mucolytic:** To reduce the viscosity of respiratory tract secretions in conditions such as chronic bronchitis, emphysema, and cystic fibrosis.
## Adult Dosing
**Acetaminophen Overdose:**
* **Standard Protocol (Oral):**
* Loading dose: 140 mg/kg as a single dose.
* Maintenance dose: 70 mg/kg every 4 hours for 17 doses (total of 72 hours).
* **Standard Protocol (Intravenous):**
* Loading dose: 150 mg/kg over 60 minutes.
* Second dose: 50 mg/kg over the next 4 hours.
* Third dose: 100 mg/kg over the next 16 hours.
* *Note: IV protocols can vary; consult local protocols. Higher doses may be used in severe overdose.*
* **Mucolytic (Nebulization):** 1-2 mL of a 20% solution or 2-4 mL of a 10% solution every 3-4 hours as needed. May be administered via intermittent aerosolization or continuously.
## Pediatric Dosing
**Acetaminophen Overdose:**
* Dosing is the same as adult dosing (140 mg/kg PO loading, 70 mg/kg PO maintenance for 17 doses OR IV protocol as above).
* **Mucolytic (Nebulization):** 1-2 mL of a 20% solution or 2-4 mL of a 10% solution every 3-4 hours as needed.
## Dose Adjustments
* **Hepatic Impairment:** No specific dose adjustment is typically required for acetaminophen overdose. However, caution is advised, and liver function should be closely monitored.
* **Renal Impairment:** No specific dose adjustment is typically required.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* *Note: For nebulized acetylcysteine, bronchospasm can occur; use with caution in patients with asthma or hyperreactive airway disease.*
## Adverse Effects
* **Common (Oral/IV for overdose):** Nausea, vomiting, rash, pruritus, fever. Anaphylactoid reactions can occur, particularly with IV administration (hypotension, bronchospasm, angioedema).
* **Common (Nebulized):** Bronchospasm, stomatitis, rhinorrhea, nausea.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its absorption. If both are administered, separate by at least 1 hour.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension. Monitor blood pressure.
## Monitoring
* **Acetaminophen Overdose:**
* Acetaminophen and salicylate levels (serial).
* Liver function tests (AST, ALT, bilirubin, INR).
* Renal function tests (BUN, creatinine).
* Glucose.
* Electrolytes.
* **Mucolytic:**
* Respiratory status.
* Pulmonary function.
## Clinical Pearls
* The efficacy of acetylcysteine for acetaminophen overdose is highest when initiated within 8-10 hours of ingestion.
* Intravenous administration may be preferred in patients with persistent vomiting or when oral administration is not feasible.
* Nebulized acetylcysteine can have an unpleasant odor.
* Bronchospasm with nebulized acetylcysteine can often be managed with co-administration of a bronchodilator.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before making clinical decisions.*
