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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucoproteins, reducing mucus viscosity. It also acts as an antidote for acetaminophen overdose by replenishing glutathione stores.
## Primary Indications
* **Acetaminophen overdose:** To prevent or mitigate liver toxicity.
* **Mucolytic agent:** To thin mucus in conditions such as chronic bronchitis, emphysema, cystic fibrosis, and bronchiectasis.
## Adult Dosing
### Acetaminophen Overdose
* **Intravenous (IV):** A standard 36-hour protocol is commonly used, starting with a loading dose of 150 mg/kg over 15 minutes, followed by 12.5 mg/kg/hr for 4 hours, then 6.25 mg/kg/hr for 16 hours. Total daily doses can exceed 1000 mg.
* **Oral:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
* *Note: Specific protocols may vary based on time of presentation and acetaminophen levels. Consult local guidelines.*
### Mucolytic Agent
* **Inhaled:** 1-10 mL of a 10-20% solution or 3-10 mL of a 20% solution, typically administered every 2-6 hours via nebulization.
* **Oral:** 200 mg (1 capsule or 5 mL of solution) two to four times daily.
* **Intravenous (IV):** For adjunctive treatment of severe bronchopulmonary disease, 300 mg in 200 mL NS every 8 hours, not to exceed 600 mg every 8 hours.
## Pediatric Dosing
### Acetaminophen Overdose
* **Intravenous (IV):** Same 36-hour protocol as adults: 150 mg/kg over 15 minutes, then 12.5 mg/kg/hr for 4 hours, then 6.25 mg/kg/hr for 16 hours. Maximum single doses are typically limited by total volume.
* **Oral:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
### Mucolytic Agent
* **Inhaled:**
* Infants and young children: 1-2 mL of a 10-20% solution every 2-6 hours.
* Older children: 3-5 mL of a 20% solution or 5-10 mL of a 10% solution every 2-6 hours.
* **Oral:** 50-100 mg two to four times daily.
## Dose Adjustments
No specific dose adjustments are typically required for hepatic or renal impairment, but caution is advised in patients with severe insufficiency.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active peptic ulcer disease (for oral formulations due to potential for gastric irritation).
## Adverse Effects
* **Common:** Bronchospasm (especially in asthmatics), nausea, vomiting, stomatitis, rash, pruritus, fever.
* **Rare but serious:** Anaphylactoid reactions (hypotension, tachycardia, dyspnea), especially with IV administration.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its effectiveness in acetaminophen overdose. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** Potentiates the vasodilatory effects and may lead to severe hypotension and headache. Monitor blood pressure closely.
## Monitoring
* **Acetaminophen Overdose:** Serum acetaminophen levels, liver function tests (AST, ALT, bilirubin, INR), renal function, glucose.
* **Mucolytic Use:** Respiratory status, sputum viscosity, incidence of bronchospasm.
## Clinical Pearls
* For IV acetylcysteine in acetaminophen overdose, rapid infusion can lead to anaphylactoid reactions. Slow infusion rates and consider premedication with antihistamines if deemed appropriate.
* Oral acetylcysteine has an unpleasant odor; dilution may improve palatability.
* Bronchospasm is a significant concern with inhaled acetylcysteine; have bronchodilators readily available.
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*Please consult the most current prescribing information and local guidelines for definitive dosing and safety recommendations.*
