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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that works by breaking disulfide bonds in mucoproteins, reducing the viscosity of mucus. It is also an antidote for acetaminophen overdose by replenishing glutathione stores.
## Primary Indications
* **Acetaminophen Overdose:** For acute acetaminophen ingestion, regardless of serum acetaminophen concentration.
* **Mucolytic Agent:** To aid in clearing mucus secretions in patients with conditions such as chronic obstructive pulmonary disease (COPD), bronchitis, emphysema, cystic fibrosis, and bronchiectasis.
## Adult Dosing
**Acetaminophen Overdose:**
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Dose:** 50 mg/kg IV infused over 16 hours.
* **Third Dose (if needed):** 50 mg/kg IV infused over 16 hours.
* **Alternative Oral Protocol (less common due to tolerability):** 140 mg/kg PO (max 1.1g), followed by 17 doses of 70 mg/kg PO (max 550mg) every 4 hours.
* **Maximum IV Dose:** Not explicitly defined by a maximum, but limited by the loading dose calculation. Consider up to 200 mg/kg over 1 hour for severe overdoses. Total infusion duration is typically 21 hours.
**Mucolytic Agent:**
* **Inhalation:** 1-10 mL of 10% solution or 2-20 mL of 20% solution via nebulization every 2-6 hours as needed. Higher concentrations may be used for more viscous secretions.
## Pediatric Dosing
**Acetaminophen Overdose:**
* Dosing is the same as adults (150 mg/kg IV over 1 hour, then 50 mg/kg IV over 16 hours, repeated if necessary). The total infusion duration is typically 21 hours.
**Mucolytic Agent:**
* **Inhalation:**
* **1 month to 6 years:** 1-2 mL of 10% solution or 1 mL of 20% solution every 2-6 hours.
* **6 years and older:** 1-10 mL of 10% solution or 2-20 mL of 20% solution every 2-6 hours.
## Dose Adjustments
No dose adjustments are typically required for renal or hepatic impairment for the acetaminophen overdose protocol. For mucolytic therapy, dose may be adjusted based on patient response and mucus viscosity.
## Contraindications
* Known hypersensitivity to acetylcysteine or any component of the formulation.
* Active untreated asthma (for inhaled preparations, use with caution).
## Adverse Effects
* **IV Administration (Acetaminophen Overdose):** Anaphylactoid reactions (rash, pruritus, urticaria, bronchospasm, angioedema, dyspnea), hypotension, tachycardia, nausea, vomiting.
* **Inhalation:** Bronchospasm, rhinorrhea, nausea, vomiting, stomatitis, urticaria.
## Key Drug Interactions
* **Activated Charcoal:** May bind acetylcysteine, reducing its oral absorption. If both are administered, separate by at least 1 hour.
## Monitoring
* **Acetaminophen Overdose:** Monitor serum acetaminophen levels to confirm resolution of toxicity and guide duration of therapy. Monitor liver function tests (ALT, AST, bilirubin) and coagulation studies (PT/INR) to assess for hepatotoxicity. Monitor vital signs and for signs of anaphylactoid reactions during IV infusion.
* **Mucolytic Therapy:** Assess airway patency, effectiveness of secretion removal, and presence of bronchospasm.
## Clinical Pearls
* For IV acetylcysteine in acetaminophen overdose, early administration is crucial for efficacy. Aim to start within 8-10 hours of ingestion.
* IV acetylcysteine may be effective even beyond 24 hours in cases of massive overdose or delayed presentation.
* Pretreatment with an H1 antagonist (e.g., diphenhydramine) may reduce the incidence of anaphylactoid reactions during IV infusion.
* Inhaled acetylcysteine can precipitate in some IV solutions; ensure compatibility if co-administered. Dilute if necessary with sterile water or saline for inhalation.
* The characteristic sulfurous odor of acetylcysteine may cause nausea and vomiting; administer with food or a flavoring agent if taken orally.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before initiating treatment.*
