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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that works by breaking disulfide bonds in mucus, reducing its viscosity. It is also the antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver toxicity.
* **Mucolytic:** To thin mucus in respiratory conditions such as chronic bronchitis, cystic fibrosis, and pneumoconiosis.
## Adult Dosing
**Acetaminophen Overdose:**
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Dose:** 50 mg/kg IV infused over 16 hours.
* **Subsequent Doses:** May be given every 4 hours for up to 72 hours if acetaminophen levels remain toxic or if clinical signs of liver injury persist.
* **Oral Dosing (if IV unavailable):** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
**Mucolytic:**
* **Nebulization:** 10% solution: 3-5 mL inhaled every 6-8 hours. 20% solution: 1-2 mL inhaled every 6-8 hours.
* **Direct Instillation (Bronchogram):** 1-2 mL of 20% solution instilled into the trachea.
* **Oral (less common for mucolytic):** 200 mg twice daily to 600 mg three times daily.
## Pediatric Dosing
**Acetaminophen Overdose:**
* Dosing is the same as adult dosing (150 mg/kg IV loading dose, followed by 50 mg/kg IV over 16 hours).
* **Oral Dosing:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
**Mucolytic:**
* **Nebulization:**
* Infants and young children: 1-2 mL of 10% solution inhaled every 2-6 hours.
* Older children: 3-5 mL of 10% solution or 1-2 mL of 20% solution inhaled every 6-8 hours.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment, though caution may be advised in severe cases of liver impairment given the primary use in acetaminophen overdose.
## Contraindications
* Hypersensitivity to acetylcysteine.
## Adverse Effects
* **IV Administration:** Anaphylactoid reactions (rash, urticaria, bronchospasm, angioedema), flushing, pruritus, headache, fever. Hypotension can occur.
* **Nebulization:** Stomatitis, nausea, vomiting, rhinorrhea, bronchospasm, urticaria.
* **Oral Administration:** Nausea, vomiting, diarrhea.
## Key Drug Interactions
* **Activated Charcoal:** Can bind acetylcysteine, reducing its absorption. Avoid concurrent administration or administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension. Monitor blood pressure closely.
## Monitoring
* **Acetaminophen Overdose:**
* Serial serum acetaminophen levels.
* Liver function tests (ALT, AST, bilirubin, INR).
* Renal function.
* Electrolytes.
* Clinical signs of encephalopathy or coagulopathy.
* **Mucolytic Use:**
* Respiratory status and sputum production.
* Bronchospasm.
## Clinical Pearls
* For IV administration in acetaminophen overdose, the antidote is most effective when given within 8 hours of ingestion. However, it should still be administered even if later, as benefit may still be seen.
* Dilute IV acetylcysteine to a concentration of no more than 10 mg/mL to reduce the risk of anaphylactoid reactions.
* Pretreatment with an antihistamine may be considered for IV administration to reduce the incidence of anaphylactoid reactions.
* Listen for adventitious breath sounds and monitor for signs of improved airway clearance with mucolytic therapy.
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*Disclaimer: This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines for definitive guidance. Local protocols may vary.*
