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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent and an antidote for acetaminophen overdose. It acts by breaking disulfide bonds in mucoproteins, reducing viscosity of mucus. As an antidote, it replenishes glutathione stores, which are depleted during acetaminophen overdose.
## Primary Indications
* Acetaminophen overdose (antidote)
* Adjunct to appropriate therapy for bronchitis, emphysema, chronic bronchitic asthma, cystic fibrosis, and other obstructive airway diseases with viscous mucus.
## Adult Dosing
**Acetaminophen Overdose:**
* **IV:** The standard protocol is a 3-bag infusion:
* **Loading Dose:** 150 mg/kg IV infused over 60 minutes.
* **Second Dose:** 50 mg/kg IV infused over the next 60 minutes.
* **Third Dose:** 100 mg/kg IV infused over the next 16 hours.
* Maximum dose is generally limited by the total volume of infusion and patient size, but specific protocols should be followed. For example, the maximum initial loading dose is typically not to exceed 150 mg/kg.
* **PO:** (Less common due to palatability and absorption variability)
* **Loading Dose:** 140 mg/kg PO.
* **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses.
**Mucolytic:**
* **PO:** 200 mg to 400 mg two to four times daily.
* **Nebulization:** 3 mL to 5 mL of 20% solution (600 mg to 1000 mg) or 6 mL to 10 mL of 10% solution (600 mg to 1000 mg) every 2 to 6 hours.
## Pediatric Dosing
**Acetaminophen Overdose (IV):**
* Dosing is the same as adult IV dosing (150 mg/kg, then 50 mg/kg, then 100 mg/kg over 16 hours). Ensure careful calculation and administration to avoid fluid overload, especially in neonates and infants.
**Acetaminophen Overdose (PO):**
* Dosing is the same as adult PO dosing (140 mg/kg, then 70 mg/kg q4h for 17 doses).
**Mucolytic:**
* **PO:** 50 mg/kg to 100 mg/kg per dose, up to 600 mg/day, divided into 2 to 4 doses.
* **Nebulization:** 1 mL to 2 mL of 20% solution (200 mg to 400 mg) or 2 mL to 4 mL of 10% solution (200 mg to 400 mg) every 2 to 6 hours.
## Dose Adjustments
No specific dose adjustments for hepatic or renal impairment are routinely recommended for the antidote use. For mucolytic use, adjustments may be guided by clinical response and patient tolerance.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active hemorrhage (relative contraindication for PO mucolytic use).
## Adverse Effects
* **IV (Antidote):** Anaphylactoid reactions (rash, pruritus, urticaria, bronchospasm, angioedema), nausea, vomiting, flushing. Anaphylactoid reactions are more common with rapid infusion and higher doses.
* **PO/Nebulization (Mucolytic):** Nausea, vomiting, stomatitis, rhinorrhea, rash, fever. Bronchospasm can occur, particularly in asthmatic patients.
## Key Drug Interactions
* **Activated Charcoal:** Decreases absorption of oral acetylcysteine. If used concurrently for acetaminophen overdose, administer oral acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension and headache.
## Monitoring
* **Acetaminophen Overdose:**
* Serial serum acetaminophen levels.
* Liver function tests (LFTs).
* Prothrombin time (PT) or international normalized ratio (INR).
* Renal function and electrolytes.
* Signs of anaphylactoid reaction.
* **Mucolytic:**
* Respiratory status (breath sounds, oxygen saturation).
* Sputum volume and consistency.
* Signs of bronchospasm.
## Clinical Pearls
* The IV formulation for acetaminophen overdose is a critical, life-saving intervention. Prompt administration is essential, especially if the time of ingestion is unknown or greater than 8-10 hours.
* Protocols for IV acetylcysteine administration (e.g., specific bag volumes and infusion rates) may vary by institution; always follow local guidelines.
* Consider premedication with an H1 antagonist (e.g., diphenhydramine) and H2 antagonist (e.g., ranitidine or famotidine) for IV acetylcysteine to mitigate anaphylactoid reactions, especially in high-risk patients.
* For oral administration as an antidote, the smell and taste can be very unpleasant. Dilution in juice or carbonated beverages may improve palatability.
* Bronchospasm with nebulized acetylcysteine can be managed by co-administration with a bronchodilator.
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*This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant clinical guidelines for definitive patient care decisions.*
