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# Acetylcysteine
## Overview
Acetylcysteine (N-acetylcysteine, NAC) is a mucolytic agent and an antidote for acetaminophen overdose. It is available in oral and intravenous formulations.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver toxicity.
* **Mucolytic:** To thin and loosen mucus in respiratory conditions like COPD and cystic fibrosis.
## Adult Dosing
**Acetaminophen Overdose:**
* **Oral:** An initial loading dose of 140 mg/kg is followed by 70 mg/kg every 4 hours for a total of 17 doses. The maximum loading dose is 140 mg/kg per dose.
* **Intravenous:** Protocols vary. A common regimen involves a 150 mg/kg loading dose over 1 hour, followed by a 12.5 mg/kg/hour infusion for 4 hours, then a 6.25 mg/kg/hour infusion for 16 hours. *Always follow local protocol or specific guidelines for IV administration, as it is complex and varies.*
**Mucolytic:**
* **Oral:** Typically 200 mg twice to four times daily.
* **Nebulized:** 1-10 mL of a 10% or 20% solution (100 mg/mL or 200 mg/mL) every 2-6 hours as needed. Some protocols use 3-5 mL of a 20% solution.
## Pediatric Dosing
**Acetaminophen Overdose:**
* **Oral:** Same as adult dosing: 140 mg/kg loading dose, then 70 mg/kg every 4 hours for 17 doses. Maximum loading dose is 140 mg/kg per dose.
* **Intravenous:** Dosing depends on age and weight, and specific IV protocols should be followed closely.
**Mucolytic:**
* **Oral:** Generally 50-200 mg twice to four times daily depending on age and condition.
* **Nebulized:** Typically 1-5 mL of a 10% or 20% solution every 2-6 hours.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment for the mucolytic indication. For acetaminophen overdose, dose adjustments are generally not needed unless the patient is unable to tolerate oral administration.
## Contraindications
* Hypersensitivity to acetylcysteine or other components.
* Acute bronchospasm (for nebulized).
## Adverse Effects
* **Common:** Nausea, vomiting, stomatitis (oral); bronchospasm, bronchorrhea (nebulized); rash, pruritus, urticaria (IV).
* **Serious:** Anaphylactoid reactions (especially with rapid IV infusion), bronchospasm.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its absorption. Separate administration by at least 1 hour.
* **Nitroglycerin:** May potentiate hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:** Serum acetaminophen levels, liver function tests (AST, ALT, bilirubin, INR), blood glucose, electrolytes, renal function.
* **Mucolytic:** Respiratory status, sputum volume and viscosity, bronchospasm.
## Clinical Pearls
* The smell of acetylcysteine can be unpleasant and may trigger nausea. Administering antiemetics may be beneficial.
* For IV administration in acetaminophen overdose, strict adherence to protocol is crucial to minimize the risk of anaphylactoid reactions. Dilution and infusion rates are important.
* For nebulized use, a suitable bronchodilator may be administered prior to acetylcysteine if bronchospasm is a concern.
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*Please verify current prescribing information and institutional protocols before use.*
