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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that decreases the viscosity of respiratory tract secretions. It is also the antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver toxicity.
* **Mucolytic:** To thin and loosen mucus in conditions such as pneumonia, bronchitis, and cystic fibrosis.
## Adult Dosing
### Acetaminophen Overdose
The standard protocol involves an initial loading dose followed by maintenance doses.
* **Intravenous (IV):**
* **Loading Dose:** 150 mg/kg IV over 1 hour.
* **Second Dose:** 50 mg/kg IV over 1 hour, 4 hours after the loading dose.
* **Third Dose:** 100 mg/kg IV over 16 hours, starting 8 hours after the second dose.
* *Total duration:* 20.25 hours.
* *Maximum dose:* 300 mg/kg over the initial 20.25 hours. Higher doses may be used in severe overdose cases per local protocol.
* **Oral:**
* **Loading Dose:** 140 mg/kg PO.
* **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses.
* *Total duration:* 72 hours.
* *Maximum dose:* 140 mg/kg per dose.
### Mucolytic
* **Nebulization:** 3 mL of a 10% or 20% solution, or 1-2 capsules of a 200 mg equivalent (inhaled via a nebulizer) every 2 to 6 hours.
* **Oral (effervescent tablets/granules):** 200 mg to 400 mg twice daily.
## Pediatric Dosing
### Acetaminophen Overdose
Dosing is the same as adult dosing based on weight.
* **Intravenous (IV):**
* **Loading Dose:** 150 mg/kg IV over 1 hour.
* **Second Dose:** 50 mg/kg IV over 1 hour, 4 hours after the loading dose.
* **Third Dose:** 100 mg/kg IV over 16 hours, starting 8 hours after the second dose.
* *Total duration:* 20.25 hours.
* **Oral:**
* **Loading Dose:** 140 mg/kg PO.
* **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses.
* *Total duration:* 72 hours.
### Mucolytic
* **Nebulization:** 1-2 mL of a 10% solution or 2-4 mL of a 20% solution every 2 to 6 hours.
## Dose Adjustments
No specific dose adjustments are typically required for hepatic or renal impairment, though caution is advised, especially in severe impairment.
## Contraindications
Hypersensitivity to acetylcysteine or any component of the formulation.
## Adverse Effects
* **Common:** Nausea, vomiting, rash, urticaria, bronchospasm (especially with nebulized formulation).
* **Less Common:** Anaphylactoid reactions, fever, dizziness, headache, dyspnea.
* **Rare:** Gastrointestinal bleeding, pulmonary hemorrhage.
## Key Drug Interactions
* **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its efficacy. Administer oral acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to increased risk of hypotension and headache.
## Monitoring
* **Acetaminophen Overdose:**
* **Liver Function Tests (LFTs):** AST, ALT, bilirubin, INR.
* **Acetaminophen and Metabolite Levels:** To assess treatment efficacy and duration.
* **Prothrombin Time (PT):** To assess for coagulopathy.
* **Mucolytic:**
* **Respiratory Status:** Breath sounds, cough, sputum production.
* **Pulmonary Function Tests:** If available.
## Clinical Pearls
* For acetaminophen overdose, IV acetylcysteine is generally preferred due to better adherence and potentially faster absorption compared to oral.
* Anaphylactoid reactions are common with IV acetylcysteine, especially during the loading dose. These are usually mild and resolve with slowing of the infusion or discontinuation.
* When nebulizing, consider using a mucolytic agent first, followed by a bronchodilator if the patient experiences bronchospasm.
* A "rotten egg" odor is characteristic of acetylcysteine and is normal.
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*Disclaimer: This information is intended for healthcare professionals. Always verify current prescribing information and consult with appropriate resources before making clinical decisions.*
