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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucoproteins, reducing the viscosity of mucus. It is also an antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen Overdose:** Treatment of acute acetaminophen ingestion to prevent hepatotoxicity.
* **Mucolytic:** Adjunct in patients with excessive, viscous mucus secretions in conditions such as chronic bronchitis, emphysema, and tracheostomy care.
## Adult Dosing
* **Acetaminophen Overdose (Oral or IV):**
* **Loading Dose:** 140 mg/kg as a single dose.
* **Maintenance Dose:** 70 mg/kg every 4 hours for 17 doses.
* The total duration of therapy is typically 72 hours.
* IV loading dose: 150 mg/kg over 60 minutes.
* IV maintenance: 50 mg/kg over 60 minutes, followed by 100 mg/kg over 18 hours.
* Maximum doses for IV are often protocol-dependent but typically around 12g over 24 hours.
* **Mucolytic:**
* **Inhalation:** 1 to 10 mL of a 20% solution or 2 to 5 mL of a 10% solution, 2 to 6 times daily.
* **Nebulization:** 3 mL to 5 mL of a 10% or 20% solution.
* **Direct Instillation:** 1 to 2 mL of a 10% or 20% solution into the tracheostomy tube every 1 to 4 hours.
## Pediatric Dosing
* **Acetaminophen Overdose (Oral or IV):**
* **Loading Dose:** 140 mg/kg as a single dose.
* **Maintenance Dose:** 70 mg/kg every 4 hours for 17 doses.
* The total duration of therapy is typically 72 hours.
* IV loading dose: 150 mg/kg over 60 minutes.
* IV maintenance: 50 mg/kg over 60 minutes, followed by 100 mg/kg over 18 hours.
* Dosing for children under 2 years old for overdose may be more complex and guided by nomograms or expert consultation.
* **Mucolytic:**
* **Inhalation:**
* 3 months to 2 years: 1 to 2 mL of a 10% solution, 2 to 6 times daily.
* 2 years and older: 1 to 10 mL of a 20% solution or 2 to 5 mL of a 10% solution, 2 to 6 times daily.
## Dose Adjustments
No specific dose adjustments are generally required for hepatic or renal impairment, but caution is advised.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active hemorrhage (for nebulized acetylcysteine).
## Adverse Effects
* **Common:** Bronchospasm, urticaria, rash, nausea, vomiting, rhinorrhea, stomatitis.
* **Serious:** Anaphylactoid reactions, bronchospasm, angioedema.
* **Acetaminophen Overdose IV:** Flushing, erythema, pruritus, urticaria, hypotension, tachycardia, bronchospasm.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb acetylcysteine, reducing its absorption when used for acetaminophen overdose. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** Potential for additive hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:**
* Acetaminophen levels and ALT/AST levels (initially and regularly during therapy).
* Prothrombin time/INR.
* Renal and liver function.
* Fluid balance.
* Signs of anaphylactoid reaction.
* **Mucolytic:**
* Airway patency and effectiveness of secretion removal.
* Bronchospasm.
## Clinical Pearls
* For acetaminophen overdose, treatment should be initiated empirically if acetaminophen levels are not immediately available and the history of ingestion is suspicious or unknown.
* The antidote is most effective when initiated within 8 hours of acetaminophen ingestion.
* When administered intravenously for acetaminophen overdose, acetylcysteine can cause anaphylactoid reactions. Pretreatment with an antihistamine may be considered, and close monitoring for adverse reactions is crucial.
* For mucolytic use, hydration is important to help thin secretions.
* Acetylcysteine solutions can oxidize in air, so use freshly prepared solutions. The characteristic sulfurous odor is normal.
**Disclaimer:** This information is intended for healthcare professionals. Always consult the current official prescribing information and relevant clinical guidelines before making any treatment decisions. Dosing may vary based on local protocols and individual patient factors.
