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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent and the specific antidote for acetaminophen (paracetamol) toxicity. It acts as a glutathione precursor, supporting the detoxification of the reactive metabolite NAPQI.
## Primary Indications
* **Acetaminophen Overdose:** Antidote for hepatotoxicity.
* **Mucolytic Therapy:** Adjunct in patients with abnormal, viscid, or inspissated mucous secretions (e.g., COPD, cystic fibrosis, pneumonia).
## Adult Dosing
* **Acetaminophen Overdose (IV):** Typically administered as a 3-bag protocol (21-hour infusion).
* Loading: 150 mg/kg over 60 minutes.
* Second dose: 50 mg/kg over 4 hours.
* Third dose: 100 mg/kg over 16 hours.
* *Note: Local protocols regarding duration and weight-based adjustments may vary.*
* **Acetaminophen Overdose (Oral):** Loading dose 140 mg/kg followed by 70 mg/kg every 4 hours for 17 doses.
* **Mucolytic:** 600–1200 mg daily in 2–4 divided doses (nebulized or oral).
## Pediatric Dosing
* **Acetaminophen Overdose:** Same weight-based dosing as adults. Requires strict adherence to concentration-specific dilution protocols to avoid fluid overload.
* **Mucolytic:** 3–5 mL of 20% solution or 6–10 mL of 10% solution via nebulizer 3–4 times daily.
## Dose Adjustments
* **Hepatic Impairment:** No specific adjustment for mucolytic use, but critical for overdose management (prolonged infusions may be required if liver enzymes remain elevated).
* **Renal Impairment:** No specific adjustment necessary.
## Contraindications
* Hypersensitivity to acetylcysteine.
* Oral administration is contraindicated in patients with esophageal varices or high risk of GI hemorrhage.
## Adverse Effects
* **IV/Systemic:** Anaphylactoid reactions (flushing, hypotension, wheezing, rash, angioedema)—most common during the loading dose.
* **Inhalation:** Bronchospasm (use a beta-agonist concurrently if needed), stomatitis, nausea, rhinorrhea.
* **Oral:** Severe nausea, vomiting, diarrhea.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb acetylcysteine. Administer charcoal first; if charcoal is given, delay acetylcysteine for 1–2 hours or increase dose.
* **Antibiotics:** Physical incompatibility exists; do not mix nebulized acetylcysteine with antibiotics (e.g., tetracyclines, erythromycin).
## Monitoring
* **Overdose:** Serum acetaminophen levels, AST/ALT, bilirubin, PT/INR, creatinine, and electrolytes.
* **Clinical:** Monitor for signs of the "anaphylactoid triad" (flushing, tachycardia, hypotension) during IV infusion. Monitor respiratory status for bronchospasm during inhalation.
## Clinical Pearls
* **Smell:** Oral/inhalation formulations have a strong sulfur (rotten egg) odor; inform patients/caregivers to improve adherence.
* **Bronchospasm:** Always monitor respiratory effort in asthma patients undergoing nebulization, as acetylcysteine may induce bronchospasm.
* **Protocol Dependency:** Dosing for acetaminophen overdose is highly protocol-dependent (e.g., Rumack-Matthew nomogram use). Always consult your institution's specific toxicology/poison center guidelines.
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*Disclaimer: This information is for educational purposes only. Clinical practice varies by institution and region. Always consult your pharmacy department, current clinical guidelines, and the manufacturer’s package insert before prescribing or administering medication.*
