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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent and a precursor to glutathione. It acts by splitting disulfide bonds in mucoproteins (lowering mucus viscosity) and replenishing glutathione stores, which is critical for neutralizing the toxic metabolite of acetaminophen (NAPQI).
## Primary Indications
* **Acetaminophen overdose:** Antidote for hepatotoxicity.
* **Mucolytic therapy:** Adjunct in bronchopulmonary disorders (e.g., COPD, cystic fibrosis) characterized by abnormal, viscid secretions.
* **Renal protection:** Prevention of contrast-induced nephropathy (evidence is inconsistent; clinical utility remains debated).
## Adult Dosing
* **Acetaminophen Overdose (IV Protocol - 21h regimen):**
* Loading dose: 150 mg/kg IV over 60 minutes.
* Second dose: 50 mg/kg IV over 4 hours.
* Third dose: 100 mg/kg IV over 16 hours.
* **Mucolytic (Inhalation):** 1–10 mL of 20% solution or 2–20 mL of 10% solution via nebulizer every 2–6 hours as needed.
* **Contrast Nephropathy:** 600 mg PO twice daily for 2 days (4 doses total), beginning the day before contrast exposure.
## Pediatric Dosing
* **Acetaminophen Overdose (IV):** Identical to adult 21-hour weight-based regimen.
* **Mucolytic (Inhalation):**
* Infants: 1–2 mL of 10% solution every 6–8 hours.
* Children: 2–6 mL of 10% solution (or 1–3 mL of 20%) every 6–8 hours.
## Dose Adjustments
* **Hepatic/Renal Impairment:** No standard dose reduction required for mucolytic use. For acetaminophen overdose, therapy must be guided by serum drug levels and liver function tests, regardless of baseline organ impairment.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* For oral/inhalation: bronchospasm (use with caution in asthmatics).
## Adverse Effects
* **IV Administration:** Anaphylactoid reactions (flushing, urticaria, angioedema, hypotension, bronchospasm) often associated with the loading dose.
* **Inhalation:** Stomatitis, nausea, vomiting, fever, rhinorrhea, and bronchospasm (more common with 20% solution).
* **General:** Unpleasant odor (sulfur-like).
## Key Drug Interactions
* **Activated Charcoal:** May adsorb acetylcysteine. Administer charcoal at least 1 hour prior to oral acetylcysteine.
* **Incompatibility:** Avoid mixing with iron, copper, or rubber/metal components in nebulizers (use glass, plastic, or stainless steel).
## Monitoring
* **Acetaminophen Overdose:** Serum acetaminophen levels, AST/ALT, bilirubin, PT/INR, creatinine, and electrolytes. Monitor for signs of anaphylactoid reaction throughout the loading dose.
* **Mucolytic:** Monitor respiratory status, cough effectiveness, and volume/consistency of sputum.
## Clinical Pearls
* **Anaphylactoid Reaction Management:** If a reaction occurs during IV infusion, pause the infusion. Antihistamines, corticosteroids, or epinephrine may be indicated based on severity before resuming at a slower rate.
* **Nebulization:** Should be used with a bronchodilator if bronchospasm occurs, as acetylcysteine alone can increase airway resistance.
* **Accuracy:** Ensure strict adherence to weight-based calculations in pediatric patients to avoid hyponatremia/fluid overload during IV infusion.
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*Disclaimer: This information is for educational purposes only. Clinical protocols for acetaminophen overdose (e.g., Rumack-Matthew nomogram/local hospital protocols) vary. Always verify specific dosing, safety, and contraindications against institutional guidelines and current FDA-approved prescribing information before administration.*
