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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that also serves as an antidote for acetaminophen overdose. It works by breaking disulfide bonds in mucus, reducing its viscosity, and by replenishing glutathione stores depleted by acetaminophen toxicity.
## Primary Indications
1. **Acetaminophen Overdose:** Treatment of acetaminophen overdose to prevent or reduce liver damage.
2. **Mucolytic:** Adjunct therapy for patients with difficulty clearing mucus secretions from the airways, such as in bronchitis, emphysema, pneumonia, and cystic fibrosis.
## Adult Dosing
* **Acetaminophen Overdose (Oral or IV):**
* **Loading Dose:** 140 mg/kg PO or IV, followed by 70 mg/kg PO or IV every 4 hours for 17 doses (total of 18 doses).
* **Maximum Dose:** Dosing regimens should be followed strictly; however, IV loading doses up to 150 mg/kg over 1 hour have been used in protocolized treatment. Higher doses may be associated with anaphylactoid reactions.
* **Mucolytic (Inhaled):**
* 3-5 mL of 20% solution or 6-10 mL of 10% solution, nebulized every 3-4 hours.
* **Maximum Dose:** Not well-defined for chronic use; adjust based on patient response and tolerance.
## Pediatric Dosing
* **Acetaminophen Overdose (Oral or IV):**
* **Loading Dose:** 140 mg/kg PO or IV, followed by 70 mg/kg PO or IV every 4 hours for 17 doses (total of 18 doses).
* **Maximum Dose:** Pediatric dosing follows the same weight-based calculation. For IV, consider maximum concentrations to avoid fluid overload.
* **Mucolytic (Inhaled):**
* 1-3 mL of 20% solution or 2-6 mL of 10% solution, nebulized every 3-4 hours.
* **Maximum Dose:** Not well-defined for chronic use; adjust based on patient response and tolerance.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically required for renal impairment, but caution is advised.
* **Hepatic Impairment:** No specific dose adjustment is typically required for hepatic impairment, but caution is advised, especially in the context of acetaminophen overdose where liver function is compromised.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active untreated asthma (for inhaled formulations).
## Adverse Effects
* **Common (IV for overdose):** Anaphylactoid reactions (rash, pruritus, urticaria, bronchospasm, angioedema, hypotension), nausea, vomiting.
* **Common (Inhaled):** Bronchospasm, nausea, vomiting, rhinorrhea, stomatitis.
* **Rare:** Hemorrhage (associated with mucoid impaction), drowsiness.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its absorption. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension and headache.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels (obtain at 4 hours post-ingestion and serially).
* Liver function tests (AST, ALT, bilirubin, INR) – baseline and daily for at least 72 hours.
* Renal function and electrolytes.
* For IV administration: Vital signs, signs of anaphylaxis.
* **Mucolytic:**
* Respiratory status (lung sounds, sputum production, work of breathing).
* Bronchospasm.
## Clinical Pearls
* The oral antidote regimen for acetaminophen overdose is generally preferred due to lower rates of anaphylactoid reactions compared to IV administration, though absorption may be delayed or reduced by vomiting.
* Administer inhaled acetylcysteine with caution in patients with reactive airway disease; consider co-administration of a bronchodilator.
* Nausea and vomiting are common with oral acetylcysteine; consider administering with meals or via nasogastric tube if necessary.
* The smell of acetylcysteine is characteristically unpleasant (sulfurous).
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*Disclaimer: This information is intended for clinical decision-making support. Always consult the official prescribing information and relevant guidelines for complete and up-to-date details.*
