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# Acetylcysteine
## Overview
Acetylcysteine (N-acetyl-L-cysteine) is a derivative of the amino acid L-cysteine. It functions as a mucolytic by breaking disulfide bonds in bronchial mucus and as a hepatoprotective agent by restoring hepatic glutathione stores.
## Primary Indications
* **Acetaminophen overdose:** Antidote to prevent hepatotoxicity.
* **Mucolytic therapy:** Adjunct for pulmonary conditions associated with viscid mucus (e.g., cystic fibrosis, chronic bronchitis).
* **Renal protection:** Prevention of contrast-induced nephropathy (evidence is inconsistent; use per institutional protocol).
## Adult Dosing
* **Acetaminophen Toxicity (IV Protocol):** 300 mg/kg total dose over 21 hours.
* Loading: 150 mg/kg in 200 mL D5W over 60 mins.
* Second dose: 50 mg/kg in 500 mL D5W over 4 hours.
* Third dose: 100 mg/kg in 1000 mL D5W over 16 hours.
* **Mucolytic (Inhalation):** 3–5 mL of 20% solution or 6–10 mL of 10% solution via nebulizer 3–4 times daily.
## Pediatric Dosing
* **Acetaminophen Toxicity:** Same weight-based mg/kg protocol as adults. Use smaller fluid volumes based on age/weight to avoid fluid overload.
* **Mucolytic (Inhalation):** 1–2 mL of 20% solution or 2–4 mL of 10% solution via nebulizer 3–4 times daily.
## Dose Adjustments
* **Renal/Hepatic:** No specific adjustments for the mucolytic form. For acetaminophen toxicity, infusion rates must be strictly followed regardless of renal status; monitor for fluid overload in patients with cardiac or renal impairment.
## Contraindications
* Hypersensitivity to the active substance.
* Inhalation form is contraindicated in patients with a history of bronchospasm (use a bronchodilator pre-treatment).
## Adverse Effects
* **IV/Systemic:** Anaphylactoid reactions (flushing, rash, pruritus), nausea, vomiting, hypotension. Risk increases with rapid infusion.
* **Inhalation:** Bronchospasm, stomatitis, rhinorrhea, unpleasant odor (rotten egg smell).
## Key Drug Interactions
* **Nitroglycerin:** May enhance vasodilation due to potentiated effects on platelets and circulation; monitor for hypotension.
* **Activated Charcoal:** Acetylcysteine may bind to charcoal. If both are indicated for overdose, administer charcoal first and allow time to pass before beginning acetylcysteine.
## Monitoring
* **Acetaminophen Toxicity:** Serum acetaminophen levels (Rumack-Matthew nomogram), ALT/AST, bilirubin, PT/INR, serum creatinine/BUN, and electrolytes. Monitor for signs of anaphylaxis during loading dose.
* **Mucolytic:** Lung sounds, ease of expectoration, and respiratory effort.
## Clinical Pearls
* **Anaphylactoid Reaction:** Not a true IgE-mediated allergy; usually dose-dependent. Treat by stopping the infusion, starting antihistamines/corticosteroids, and restarting at a slower rate if the patient stabilizes.
* **Odor:** Warn patients that the sulfur smell is normal and inherent to the drug.
* **Nebulization:** Always administer a short-acting beta-agonist (e.g., albuterol) 10–15 minutes prior to inhaled acetylcysteine to prevent procedure-induced bronchospasm.
* **Protocol:** Always check institutional specific pharmacy/toxicology protocols for acetaminophen overdose, as newer "abbreviated" protocols may exist.
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*Disclaimer: This information is for educational purposes. Always verify current prescribing information, institutional protocols, and clinical guidelines before prescribing or administering medication.*
