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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is a mucolytic agent and an antidote for acetaminophen overdose. It works by breaking disulfide bonds in mucus, making it thinner and easier to clear. As an antidote, it replenishes glutathione stores depleted by acetaminophen metabolism.
## Primary Indications
* **Acetaminophen Overdose:** Treatment to prevent liver damage.
* **Mucolytic:** To thin mucus in respiratory conditions such as chronic bronchitis, emphysema, and cystic fibrosis.
## Adult Dosing
### Acetaminophen Overdose
* **Intravenous (IV):** Typically a 3-bag (or 4-bag, depending on protocol) infusion:
* **Loading Dose:** 150 mg/kg IV over 60 minutes.
* **Second Infusion:** 50 mg/kg IV over 16 hours (often as a continuous infusion).
* **Third Infusion (if needed):** 50 mg/kg IV over 16 hours.
* Maximum single dose usually 150 mg/kg. Total dose over 20 hours can exceed 400 mg/kg. Exact protocols may vary; consult local guidelines.
* **Oral:**
* **Loading Dose:** 140 mg/kg orally.
* **Subsequent Doses:** 70 mg/kg orally every 4 hours for 17 doses (total of 18 doses).
* Maximum single oral dose usually 140 mg/kg. May be administered via nasogastric tube if vomiting.
### Mucolytic
* **Oral:** 200 mg twice daily to three times daily. Higher doses up to 600 mg twice daily have been used.
* **Inhaled:** 1-10 mL of a 10-20% solution every 2-6 hours, or 3-5 mL of a 20% solution every 6-8 hours. Dosing depends on concentration and frequency; consult specific product information and institutional protocols.
* **Intravenous:** Typically reserved for acetaminophen overdose. Not a standard mucolytic regimen.
## Pediatric Dosing
### Acetaminophen Overdose
* Dosing is weight-based and follows the same IV or oral regimens as adults, adjusted for pediatric weight.
* **Intravenous (IV):** Use the 3-bag (or 4-bag) infusion described in adult dosing, calculated based on the child's weight.
* **Oral:** Use the oral regimen described in adult dosing, calculated based on the child's weight.
### Mucolytic
* **Oral:** 50-100 mg two to four times daily.
* **Inhaled:** 1-10 mL of a 10-20% solution or 3-5 mL of a 20% solution, frequency varies (e.g., every 2-6 hours). Consult specific product information and institutional protocols.
## Dose Adjustments
* No specific dose adjustments are generally required for renal or hepatic impairment in the context of acetaminophen overdose treatment, as the primary goal is to overcome the overdose toxicity. For mucolytic use, monitor for adverse effects, particularly in patients with severe hepatic or renal impairment, although formal dose adjustments are not established.
## Contraindications
* Known hypersensitivity to acetylcysteine or any component of the formulation.
* **Oral:** Active peptic ulcer disease (relative contraindication due to potential gastrointestinal irritation).
## Adverse Effects
* **Intravenous:** Anaphylactoid reactions (rash, pruritus, angioedema, bronchospasm, hypotension), flushing, fever, headache. Rare: seizures, cardiac arrest.
* **Oral:** Nausea, vomiting, diarrhea, stomatitis, rash.
* **Inhaled:** Bronchospasm (especially in asthmatics), rhinorrhea, nausea, vomiting.
## Key Drug Interactions
* **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its absorption. Administer oral acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May enhance the vasodilatory effects of nitroglycerin, potentially leading to hypotension.
* **Antitussives:** May suppress cough reflex, increasing the risk of mucus plugging when used as a mucolytic.
## Monitoring
* **Acetaminophen Overdose:** Monitor acetaminophen levels, liver function tests (AST, ALT, bilirubin, INR), and clinical status. For IV administration, monitor for anaphylactoid reactions.
* **Mucolytic Use:** Monitor respiratory status, sputum volume and consistency, and for adverse effects.
## Clinical Pearls
* The IV route for acetaminophen overdose is generally preferred over oral due to better absorption and tolerance, especially in vomiting patients.
* Anaphylactoid reactions are common with IV acetylcysteine but are usually manageable and do not necessitate immediate discontinuation unless severe. Pretreatment with an antihistamine may be considered.
* For oral administration, mixing with carbonated beverages or juices may improve palatability and reduce nausea.
* For inhaled administration, bronchospasm can be mitigated by administering a bronchodilator before acetylcysteine.
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**Disclaimer:** This information is for educational purposes and does not substitute for professional medical advice. Always consult the most current prescribing information, local protocols, and a qualified healthcare provider before making any decisions regarding medication use.
