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# Acetylcysteine
## Overview
Acetylcysteine is an mucolytic agent and an antidote for acetaminophen overdose. It works by breaking disulfide bonds in mucoproteins, reducing mucus viscosity, and replenishing glutathione stores depleted by acetaminophen metabolism.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver toxicity.
* **Mucolytic:** To thin mucus in conditions like cystic fibrosis, chronic bronchitis, and pneumonia.
## 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:** If the initial dose is vomited within 1 hour, repeat the dose. The standard 16-hour infusion is typically given as a continuous infusion after the loading dose. The total duration is generally 20-21 hours. Specific protocols may vary based on serum acetaminophen levels and time since ingestion.
**Mucolytic:**
* **Nebulized:** 3 mL of 20% solution or 6 mL of 10% solution every 3-4 hours, or as an aerosol.
* **Oral:** 200 mg (ER formulation) to 600 mg twice daily.
## Pediatric Dosing
**Acetaminophen Overdose:**
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Dose:** 50 mg/kg IV infused over 16 hours.
* The total duration is generally 20-21 hours. Specific protocols may vary based on serum acetaminophen levels and time since ingestion, particularly for neonates and infants.
**Mucolytic:**
* **Nebulized:**
* 10% solution: 1-2 mL every 2-6 hours.
* 20% solution: 1 mL every 2-6 hours.
* **Oral:** 10 mg/kg up to 200 mg 2-3 times daily. ER formulation generally not recommended for children < 12 years.
## Dose Adjustments
No dose adjustment is typically required for renal or hepatic impairment when used for acetaminophen overdose, as the metabolism and clearance are complex and toxicity is the primary concern. For mucolytic use, dose adjustments are usually based on patient tolerance and response.
## Contraindications
* Hypersensitivity to acetylcysteine.
* Use with caution in patients with asthma due to potential for bronchospasm.
## Adverse Effects
* **IV (Acetaminophen Overdose):** Anaphylactoid reactions (rash, pruritus, angioedema, bronchospasm, dyspnea, hypotension), nausea, vomiting, fever.
* **Nebulized:** Bronchospasm, stomatitis, nausea, rhinorrhea.
* **Oral:** Nausea, vomiting, diarrhea, rash.
## Key Drug Interactions
* **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its efficacy. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May potentiate the hypotensive effect of nitroglycerin.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels (at appropriate time points, usually 4 hours post-ingestion and subsequently).
* Liver function tests (AST, ALT, bilirubin, INR).
* Renal function (BUN, creatinine).
* Glucose.
* Vital signs, especially for anaphylactoid reactions.
* **Mucolytic:**
* Pulmonary function, airway clearance.
* Bronchospasm.
## Clinical Pearls
* The IV formulation for acetaminophen overdose is a life-saving antidote. Prompt administration is crucial, especially if ingestion time is unknown or >8 hours.
* Oral acetylcysteine has a characteristic sulfur odor that may be unpleasant.
* For IV use in acetaminophen overdose, monitoring for anaphylactoid reactions is essential. Diphenhydramine can be used prophylactically or to treat mild symptoms.
* Nebulized acetylcysteine can sometimes worsen bronchospasm; consider co-administration with a bronchodilator.
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*This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and local institutional protocols before making any treatment decisions.*
