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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent and an antidote for acetaminophen overdose. It works by breaking disulfide bonds in mucoproteins, reducing viscosity of mucus, and by replenishing glutathione stores depleted by acetaminophen toxicity.
## Primary Indications
* **Acetaminophen Overdose:** Treatment is most effective when initiated within 8 hours of ingestion.
* **Mucolytic Agent:** Used to thin mucus in respiratory conditions such as COPD, cystic fibrosis, and pneumonia.
## Adult Dosing
### Acetaminophen Overdose
The standard IV protocol involves a 3-bag regimen:
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Infusion:** 50 mg/kg IV infused over 4 hours.
* **Third Infusion:** 100 mg/kg IV infused over 16 hours.
* **Maximum Dose:** Typically no maximum dose is specified for the treatment of overdose, however, large doses should be monitored closely for adverse effects.
Oral dosing is also available and often involves a loading dose followed by multiple doses over 72 hours. Specific oral protocols vary and should be consulted.
### Mucolytic Agent
* **Nebulized:** 3 mL of 20% solution or 6 mL of 10% solution every 2-6 hours as needed. Alternatively, 300-600 mg nebulized every 4-12 hours.
* **Oral:** 200 mg twice daily to three times daily. 600 mg once daily.
## Pediatric Dosing
### Acetaminophen Overdose
Pediatric dosing follows the same IV regimen as adults, calculated by weight:
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Infusion:** 50 mg/kg IV infused over 4 hours.
* **Third Infusion:** 100 mg/kg IV infused over 16 hours.
Oral dosing in pediatrics also follows specific protocols, varying by age and weight.
### Mucolytic Agent
* **Nebulized:**
* Children < 1 year: 1-2 mL of 20% solution or 2-4 mL of 10% solution every 2-6 hours.
* Children > 1 year: 3 mL of 20% solution or 6 mL of 10% solution every 2-6 hours.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended, but caution is advised.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended, but caution is advised.
## Contraindications
* Known hypersensitivity to acetylcysteine.
## Adverse Effects
* **Anaphylactoid Reactions:** Bronchospasm, urticaria, angioedema, rash, pruritus, dyspnea. These are more common with IV administration and are often related to the rate of infusion.
* **Gastrointestinal:** Nausea, vomiting, diarrhea.
* **Respiratory:** Bronchorrhea, stomatitis.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb acetylcysteine, reducing its efficacy. Separate administration times if both are used.
* **Nitroglycerin:** Potential for additive hypotension.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels.
* Liver function tests (AST, ALT, bilirubin, INR).
* Renal function (BUN, creatinine).
* Electrolytes.
* Clinical signs of liver toxicity.
* **Mucolytic Agent:**
* Respiratory status, effectiveness in thinning secretions.
* Bronchospasm, especially in patients with reactive airway disease.
## Clinical Pearls
* For IV acetylcysteine, pre-treatment with an H1 antagonist (e.g., diphenhydramine) may help mitigate anaphylactoid reactions.
* Rapid infusion of IV acetylcysteine can lead to hypotension and anaphylactoid reactions. Infusion rates should be strictly adhered to.
* The characteristic sulfurous odor of acetylcysteine is normal and not indicative of a compromised product.
* For nebulized acetylcysteine, dilution with sterile water for injection or saline may be necessary if a more dilute solution is desired, though this is not always required.
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*This information is intended for healthcare professionals. Always consult the official prescribing information and relevant guidelines for complete details, including specific dosages and contraindications, as these can vary based on the formulation, patient factors, and local protocols. This document does not replace clinical judgment.*
