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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 mucus viscosity, and by replenishing glutathione stores depleted by toxic acetaminophen metabolites.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce the severity of hepatotoxicity.
* **Mucolytic Agent:** For conditions involving thick, tenacious mucus (e.g., cystic fibrosis, COPD, pneumonia).
## Adult Dosing
**Acetaminophen Overdose:**
* **Standard Protocol (Oral or IV):** Typically involves an initial loading dose followed by subsequent doses over 24 hours.
* **Oral:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
* **IV:** 150 mg/kg IV over 1 hour, followed by 50 mg/kg IV over 4 hours, then 100 mg/kg IV over 16 hours. (Maximum infusion rate is typically 12.5 g/hour).
* **Dosing may vary based on nomogram (e.g., Rumack-Matthew) and timing of presentation.**
**Mucolytic Agent:**
* **Inhalation:** 3-5 mL of 20% solution or 6-10 mL of 10% solution nebulized every 4-12 hours.
* **Intratracheal:** 1-2 mL of 10-20% solution every 1-4 hours.
## Pediatric Dosing
**Acetaminophen Overdose:**
* **Oral:** Same as adult: 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
* **IV:** Same as adult: 150 mg/kg IV over 1 hour, followed by 50 mg/kg IV over 4 hours, then 100 mg/kg IV over 16 hours.
* **Dosing may vary based on nomogram and timing of presentation.**
**Mucolytic Agent:**
* **Inhalation:**
* < 1 year: 1 mL of 10% solution nebulized every 2-6 hours.
* 1-6 years: 2-4 mL of 10% solution or 1-2 mL of 20% solution nebulized every 4-12 hours.
* > 6 years: 3-5 mL of 20% solution or 6-10 mL of 10% solution nebulized every 4-12 hours.
## Dose Adjustments
No specific dose adjustments are generally required for hepatic or renal impairment, but caution is advised, especially in severe cases of overdose management.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active bronchospasm (for inhalation use).
## Adverse Effects
* **IV (Overdose):** Anaphylactoid reactions (rash, urticaria, pruritus, angioedema, bronchospasm, dyspnea, hypotension) are most common. Nausea and vomiting can also occur.
* **Inhalation:** Bronchospasm, rhinorrhea, nausea, vomiting, stomatitis.
## Key Drug Interactions
* **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its absorption. Separate administration by at least 1 hour.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension and headache. Monitor closely.
## Monitoring
* **Acetaminophen Overdose:**
* Liver function tests (ALT, AST, bilirubin, INR) at baseline and then every 24 hours for at least 72 hours.
* Acetaminophen levels.
* Renal function and electrolytes.
* Clinical signs of hepatotoxicity.
* **Mucolytic Use:**
* Pulmonary status (respiratory rate, breath sounds, oxygen saturation).
* Bronchospasm.
## Clinical Pearls
* For acetaminophen overdose, timely administration is crucial; effectiveness decreases significantly if treatment is initiated more than 8-10 hours after ingestion.
* IV acetylcysteine requires careful monitoring for anaphylactoid reactions, especially during the initial infusion. Pretreatment with an H1 antagonist may be considered.
* Dilute IV acetylcysteine in dextrose 5% in water (D5W) or normal saline (NS) for infusion to reduce the risk of fluid overload.
* For inhalation, acetylcysteine may worsen bronchospasm in patients with asthma or reactive airway disease. Co-administration of a bronchodilator may be necessary.
* The odor of acetylcysteine is unpleasant (sulfurous) but does not correlate with efficacy or safety.
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*This information is intended for healthcare professionals. Always consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions.*
