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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent and an antidote for acetaminophen overdose.
## Primary Indications
* Acetaminophen overdose
* Adjunct in management of respiratory conditions associated with viscous or excessive mucus secretions (e.g., bronchitis, emphysema, cystic fibrosis, pneumonia)
## Adult Dosing
**Acetaminophen Overdose:**
* **IV:** Typically a 3-bag, 72-hour protocol.
* **Loading dose:** 150 mg/kg (maximum 150 mg/kg or 15 g) infused over 60 minutes.
* **Second dose:** 50 mg/kg (maximum 50 mg/kg or 12.5 g) infused over the next 60 minutes.
* **Subsequent doses:** 100 mg/kg (maximum 100 mg/kg or 25 g) infused over the next 16 hours.
* **PO:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses. Maximum dose typically 140 mg/kg per dose.
* **Note:** IV route is generally preferred due to better bioavailability and reduced emesis.
**Respiratory Conditions:**
* **PO:** 200 mg to 400 mg twice or three times daily.
* **Nebulized:** 1 to 10 mL of 10% solution (100 mg/mL) or 2 to 5 mL of 20% solution (200 mg/mL) every 2 to 6 hours as needed.
## Pediatric Dosing
**Acetaminophen Overdose:**
* **IV:** Dosing follows the same protocol as adults (150 mg/kg, 50 mg/kg, 100 mg/kg over 72 hours). Maximum doses per bag should be calculated based on patient weight.
* **PO:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
**Respiratory Conditions:**
* **PO:** 50 mg/kg twice daily or 100 mg three times daily.
* **Nebulized:** Generally 1 mL of 20% solution (200 mg/mL) or 2-5 mL of 10% solution (100 mg/mL) every 2-6 hours. Concentration may be diluted with sterile water for inhalation if needed.
## Dose Adjustments
* No specific dose adjustment is typically required for renal or hepatic impairment for the antidote indication. However, prolonged use for respiratory conditions may warrant closer monitoring in these populations.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
## Adverse Effects
* **IV:** Anaphylactoid reactions (rash, pruritus, bronchospasm, angioedema), hypotension, tachycardia, nausea, vomiting.
* **PO:** Nausea, vomiting, stomatitis, gastrointestinal upset.
* **Nebulized:** Bronchospasm, rhinorrhea, stomatitis, nausea.
## Key Drug Interactions
* **Activated charcoal:** Can bind to oral acetylcysteine, reducing its absorption. If both are used, separate administration by at least 1 hour.
* **Nitroglycerin:** Potential for additive hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:** Serum acetaminophen levels, liver function tests (ALT, AST, bilirubin, INR), glucose, electrolytes, renal function, and clinical status (especially for anaphylactoid reactions).
* **Respiratory Conditions:** Respiratory status, sputum viscosity, frequency of exacerbations.
## Clinical Pearls
* For IV administration in acetaminophen overdose, monitor closely for anaphylactoid reactions, especially during the initial loading dose. Pretreatment with antihistamines may be considered in some protocols.
* N-acetylcysteine is most effective when administered within 8 to 10 hours of acetaminophen ingestion.
* Diluting nebulized acetylcysteine may reduce airway irritation.
* The odor of acetylcysteine is characteristically sulfurous; this is normal.
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*This information is intended for clinical use and does not substitute for professional medical advice. Always consult the most current prescribing information and relevant institutional protocols before administering any medication.*
