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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucoproteins, reducing viscosity. It also acts as an antidote for acetaminophen overdose by replenishing glutathione stores.
## Primary Indications
* Acetaminophen overdose
* Mucolytic for conditions with thick mucus secretions (e.g., cystic fibrosis, COPD, pneumonia)
## Adult Dosing
* **Acetaminophen Overdose:**
* **Loading Dose:** 150 mg/kg IV over 1 hour.
* **Second Dose:** 50 mg/kg IV over 3 hours.
* **Subsequent Doses:** 100 mg/kg IV over 16 hours (total 17-hour infusion).
* *Note:* Dosing may be adjusted based on acetaminophen levels and time since ingestion. Some centers use a 36-hour protocol. Oral administration is an alternative, particularly for milder ingestions or if IV access is difficult, but is associated with a higher incidence of nausea and vomiting.
* **Mucolytic:**
* **Inhaled:** 200 mg every 4-12 hours. Higher concentrations (up to 1000 mg) may be used in some protocols.
* **Oral (Effervescent Tablets):** 200 mg 2-3 times daily.
* **Nebulized (IV preparation):** 1-10 mL of 10-20% solution every 2-6 hours, depending on protocol and patient tolerance.
## Pediatric Dosing
* **Acetaminophen Overdose:** Dosing is weight-based and identical to adult dosing. Maximum loading dose typically capped at 150 mg/kg.
* **Mucolytic:**
* **Inhaled:** 50-100 mg every 4-12 hours.
* **Nebulized (IV preparation):** Dosing varies significantly by age and protocol. For example, 1 month to 1 year: 0.5-1 mL of 20% solution every 2-6 hours. Children 1-12 years: 1-2 mL of 20% solution every 2-6 hours.
## Dose Adjustments
No specific dose adjustments are generally required for renal or hepatic impairment, though caution and close monitoring are advised.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active bronchospasm (for inhaled formulations).
## Adverse Effects
* **Common:** Nausea, vomiting, stomatitis, rash, pruritus.
* **Less Common:** Bronchospasm (especially in asthmatics receiving inhaled), rhinorrhea, drowsiness, headache.
* **Rare:** Anaphylactoid reactions (more common with IV administration).
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its efficacy. Administer charcoal at least 1 hour before or after oral acetylcysteine.
* **Nitroglycerin:** Potentiated hypotensive effect.
## Monitoring
* **Acetaminophen Overdose:** Serum acetaminophen levels, liver function tests (LFTs), prothrombin time (PT)/international normalized ratio (INR), glucose, electrolytes, and renal function. Clinical assessment for signs of hepatotoxicity.
* **Mucolytic:** Respiratory status, effectiveness in clearing secretions, and adverse effects.
## Clinical Pearls
* The characteristic "rotten egg" odor is normal.
* For IV administration in acetaminophen overdose, anaphylactoid reactions are common and can be severe but are often manageable with antihistamines and bronchodilators. Discontinuation of the infusion is rarely necessary.
* Oral formulations are often associated with significant gastrointestinal upset.
* When used as a mucolytic, the effectiveness can be variable.
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*Please verify the current prescribing information and institutional protocols for definitive dosing and administration guidelines.*
