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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is an antidote for acetaminophen overdose and a mucolytic agent. It replenishes hepatic glutathione stores depleted by acetaminophen metabolism. As a mucolytic, it breaks disulfide bonds in mucus, reducing viscosity.
## Primary Indications
* Acetaminophen (APAP) overdose
* Mucolytic for conditions with thick mucus secretions (e.g., cystic fibrosis, COPD, pneumonia)
## Adult Dosing
### Acetaminophen Overdose
* **Intravenous (IV):** Typically administered as a 2-bag, 21-hour protocol.
* **Loading Dose:** 150 mg/kg IV infused over 60 minutes.
* **Second Infusion:** 50 mg/kg IV infused over 60 minutes.
* **Third Infusion:** 100 mg/kg IV infused over 18 hours.
* **Maximum Dose:** Total daily dose not to exceed 200 mg/kg. Protocols may vary; consult local guidelines.
* **Oral:** Historically used, less common now due to IV efficacy and tolerability.
* **Loading Dose:** 140 mg/kg PO.
* **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses (total of 18 doses).
* **Maximum Dose:** 140 mg/kg per dose. Higher doses may be used in specific circumstances, consult guidelines.
### Mucolytic
* **Inhalation:** 1-10 mL of 20% solution or 2-20 mL of 10% solution nebulized every 2-6 hours as needed.
* **Oral:** 200-600 mg BID or TID.
## Pediatric Dosing
### Acetaminophen Overdose
* **Intravenous (IV):** Same as adult dosing (150 mg/kg, 50 mg/kg, 100 mg/kg over specified times). Maximum total daily dose not to exceed 200 mg/kg. Protocols may vary; consult local guidelines.
* **Oral:** Same as adult dosing (140 mg/kg, then 70 mg/kg every 4 hours for 17 doses).
### Mucolytic
* **Inhalation:**
* Infants and children < 2 years: 1-2 mL of 20% solution or 2-4 mL of 10% solution nebulized 2-4 times daily.
* Children > 2 years: 1-10 mL of 20% solution or 2-20 mL of 10% solution nebulized every 2-6 hours as needed.
* **Oral:** 50 mg/kg BID; maximum 600 mg/day.
## Dose Adjustments
No specific dose adjustments are typically required for hepatic or renal impairment, although caution is advised.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active, untreated asthma (inhalation).
## Adverse Effects
* **IV:** Anaphylactoid reactions (rash, pruritus, angioedema, bronchospasm), nausea, vomiting, flushing. Risk is higher with rapid infusion.
* **Inhalation:** Bronchospasm, nausea, vomiting, stomatitis, rhinitis.
* **Oral:** Nausea, vomiting, diarrhea, abdominal discomfort.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its efficacy. Separate administration by at least 1 hour.
* **Nitroglycerin:** Concomitant use may potentiate hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels (obtain at least 4 hours post-ingestion, and repeat as needed).
* Liver function tests (LFTs), INR, glucose, electrolytes, renal function (especially if initial levels are high or delayed presentation).
* Clinical signs and symptoms of acetaminophen toxicity.
* **Mucolytic:**
* Pulmonary status (breath sounds, oxygen saturation).
* Sputum viscosity and ease of expectoration.
## Clinical Pearls
* For IV acetaminophen overdose, prompt administration regardless of presentation time is crucial. Toxicity is less likely if APAP level is below the treatment nomogram line.
* Anaphylactoid reactions to IV NAC are common but usually managed by slowing the infusion rate and administering antihistamines. Discontinuation is rarely necessary.
* The smell of acetylcysteine (rotten eggs) is normal and indicates drug integrity.
* For mucolytic use, premedication with a bronchodilator may be necessary in patients with reactive airway disease.
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***Disclaimer:** This information is intended for healthcare professionals and does not substitute for comprehensive drug information resources. Always consult the most current prescribing information and institutional protocols before administering any medication.*
