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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent and an antidote to acetaminophen overdose. It also has antioxidant properties.
## Primary Indications
* **Acetaminophen Overdose:** Antidote.
* **Mucolytic:** To thin mucus in conditions such as cystic fibrosis, COPD, and pneumonia.
## Adult Dosing
* **Acetaminophen Overdose:**
* **Intravenous (IV):** A 3-bag, 21-hour infusion is standard.
* Loading dose: 150 mg/kg IV over 60 minutes.
* Second infusion: 50 mg/kg IV over 12 hours (max 12.5 g/day).
* Third infusion: 100 mg/kg IV over 12 hours (max 12.5 g/day).
* *Note:* For severe reactions, continue infusion at slower rates. Max total dose 30 g.
* **Oral (PO):** A 72-hour protocol.
* Loading dose: 140 mg/kg PO (max 13 g).
* Subsequent doses: 70 mg/kg PO every 4 hours for 17 doses (max 6.5 g per dose).
* *Note:* If vomiting occurs within 1 hour of administration, repeat the dose. Antiemetics may be necessary.
* **Mucolytic:**
* **Nebulization:** 3 mL to 5 mL of 20% solution or 6 mL to 10 mL of 10% solution every 3 to 4 hours.
* **Nebulization (Thick Mucus):** 1 mL of 20% solution or 2 mL of 10% solution every 3 to 4 hours (may be increased as tolerated).
* **Intratracheal:** 1 mL to 2 mL of 10% or 20% solution every 1 to 4 hours.
## Pediatric Dosing
* **Acetaminophen Overdose (IV):** Same as adult dosing (150 mg/kg, then 50 mg/kg, then 100 mg/kg). Weight-based dosing is crucial for pediatric patients.
* **Acetaminophen Overdose (PO):** Same as adult dosing (140 mg/kg, then 70 mg/kg).
* **Mucolytic:**
* **Nebulization:** 1 mL of 20% solution or 2 mL of 10% solution every 3 to 4 hours. For infants, doses may be lower and administered over a longer period. Consult institutional protocols.
## Dose Adjustments
* No dose adjustments are typically needed for renal or hepatic impairment for the antidote indication.
* For mucolytic use, doses may be adjusted based on patient tolerance and response.
## Contraindications
* Hypersensitivity to acetylcysteine.
## Adverse Effects
* **IV Acetaminophen Antidote:** Anaphylactoid reactions (rash, pruritus, bronchospasm, angioedema, hypotension), fever, nausea, vomiting. Bronchospasm is a significant concern.
* **Nebulized Acetylcysteine:** Nausea, vomiting, stomatitis, rhinorrhea, bronchospasm, urticaria. Bronchospasm may be exacerbated in patients with asthma or hyperreactive airways.
## Key Drug Interactions
* **Activated Charcoal:** Can bind acetylcysteine if given orally, reducing absorption. Separate administration by at least 1 hour.
* **Nitroglycerin:** Potential for additive hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels (obtain at least 4 hours post-ingestion and again 12-24 hours later to assess the need for continued treatment).
* Liver function tests (AST, ALT, bilirubin, INR) starting at 24 hours post-ingestion and continuing daily for up to 7 days.
* Monitor for signs of anaphylactoid reaction.
* Glucose levels (especially with IV infusion).
* **Mucolytic:**
* Respiratory status, including airway patency and effectiveness of secretion removal.
* Pulmonary function tests may be considered.
* Monitor for bronchospasm.
## Clinical Pearls
* The IV route for acetaminophen overdose is preferred due to better efficacy and fewer gastrointestinal side effects compared to the oral route, especially in patients who are vomiting.
* Administer IV acetylcysteine slowly initially to reduce the risk of anaphylactoid reactions. Pretreatment with an antihistamine may be considered.
* For nebulized acetylcysteine, it can have an unpleasant odor, which may lead to nausea and vomiting.
* Always check the concentration of the acetylcysteine solution before administration.
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*This information is intended for clinical decision-making and does not replace professional medical advice. Always consult the current prescribing information and relevant clinical guidelines for the most up-to-date and complete details.*
