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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent and an antidote for acetaminophen overdose. It is available as an inhalation solution, an oral solution, and an intravenous (IV) formulation.
## Primary Indications
* **Acetaminophen Overdose:** Reversal of hepatotoxicity.
* **Mucolytic Agent:** For conditions with thick, viscous mucus, such as chronic bronchitis, cystic fibrosis, and emphysema.
## Adult Dosing
**Acetaminophen Overdose (IV):**
* **Loading Dose:** 150 mg/kg IV over 1 hour.
* **Second Infusion:** 50 mg/kg IV over 16 hours.
* **Third Infusion (if needed):** 50 mg/kg IV over 16 hours.
* **Total duration:** Minimum 21 hours. Some protocols may extend duration based on acetaminophen levels.
**Acetaminophen Overdose (Oral):**
* **Loading Dose:** 140 mg/kg PO.
* **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses (total 72 hours).
**Mucolytic (Inhaled):**
* **Standard Dose:** 3 mL to 5 mL of a 20% solution or 6 mL to 10 mL of a 10% solution via nebulizer every 3 to 4 hours.
* **Alternative:** 1-2 mL of 20% solution or 2-4 mL of 10% solution every 3 to 4 hours.
## Pediatric Dosing
**Acetaminophen Overdose (IV):**
* Dosing is the same as adult: 150 mg/kg IV over 1 hour, followed by 50 mg/kg IV over 16 hours, and potentially a third infusion of 50 mg/kg IV over 16 hours.
**Acetaminophen Overdose (Oral):**
* Dosing is the same as adult: 140 mg/kg PO once, followed by 70 mg/kg PO every 4 hours for 17 doses.
**Mucolytic (Inhaled):**
* **Standard Dose:** 1 mL to 2 mL of a 20% solution or 2 mL to 4 mL of a 10% solution via nebulizer every 3 to 4 hours.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended for renal impairment, but caution is advised.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended for hepatic impairment, but caution is advised, especially in acetaminophen overdose.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active bronchospasm (for inhaled formulations).
## Adverse Effects
* **Common (Inhaled):** Bronchospasm, bronchoconstriction, nausea, vomiting, stomatitis, rhinorrhea.
* **Common (IV):** Anaphylactoid reactions (rash, pruritus, urticaria, angioedema, bronchospasm, dyspnea, hypotension), fever, chills. Nausea and vomiting can occur, especially with rapid infusion.
* **Common (Oral):** Nausea, vomiting, diarrhea.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb acetylcysteine, reducing its oral absorption. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** Concurrent use may potentiate hypotension and headache.
## Monitoring
* **Acetaminophen Overdose:**
* Serial serum acetaminophen levels.
* Liver function tests (ALT, AST, bilirubin, INR).
* Renal function.
* Glucose.
* Electrolytes.
* **Mucolytic:**
* Pulmonary function tests.
* Signs and symptoms of mucus obstruction.
## Clinical Pearls
* **IV Formulation:** Dilute in 5% dextrose or 0.9% sodium chloride for IV infusion to reduce risk of anaphylactoid reactions. Closely monitor for signs of hypersensitivity.
* **Inhaled Formulation:** May cause bronchospasm, especially in patients with asthma. Pretreatment with a bronchodilator may be necessary.
* **Smell:** Acetylcysteine has a characteristic sulfurous odor which is not indicative of degradation.
* **Oral Formulation:** The taste can be unpleasant; mixing with juice or carbonated beverages may improve palatability.
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*Please verify current prescribing information for the most up-to-date and complete drug details.*
