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# Acetylcysteine
## Overview
Acetylcysteine (N-acetyl-L-cysteine) acts as a mucolytic by splitting disulfide bonds in mucoproteins and as a precursor to glutathione, essential for detoxifying the toxic metabolite (NAPQI) of acetaminophen.
## Primary Indications
* **Acetaminophen overdose:** Management of acute ingestion.
* **Mucolytic therapy:** Adjunctive therapy for abnormal, viscid, or inspissated mucous secretions (e.g., bronchitis, COPD, cystic fibrosis).
* **Contrast-induced nephropathy (off-label):** Prevention of renal injury in high-risk patients.
## Adult Dosing
* **Acetaminophen Overdose (IV):** Three-bag regimen (FDA protocol). Loading dose: 150 mg/kg over 60 mins; Second dose: 50 mg/kg over 4 hours; Third dose: 100 mg/kg over 16 hours.
* **Acetaminophen Overdose (Oral):** Loading dose: 140 mg/kg; followed by 70 mg/kg every 4 hours for 17 doses.
* **Mucolytic (Nebulized):** 3–5 mL of 20% solution or 6–10 mL of 10% solution administered 3–4 times daily.
## Pediatric Dosing
* **Acetaminophen Overdose:** Follows the same weight-based per kg dosing as adults. *Note: Strict adherence to body weight calculation is required to avoid fluid overload in infants.*
* **Mucolytic (Nebulized):** 3–5 mL of 20% solution or 6–10 mL of 10% solution administered 3–4 times daily.
## Dose Adjustments
* **Renal/Hepatic:** No standardized adjustments for renal/hepatic impairment in overdose management; however, patients with hepatic failure are at higher risk for complications. Clinical response and serum concentrations should dictate duration.
## Contraindications
* **Hypersensitivity:** History of severe reaction to acetylcysteine.
* **Oral/Nebulized:** Airway obstruction or inability to clear secretions (mucolytic effect may increase volume of secretions beyond patient's ability to expectorate).
## Adverse Effects
* **IV (Anaphylactoid):** Flushing, pruritus, urticaria, angioedema, hypotension, and bronchospasm (most common during the loading dose).
* **Inhalation:** Bronchospasm (pre-treat with short-acting beta-agonists), stomatitis, rhinorrhea, nausea, and unpleasant odor (rotten eggs/sulfur).
## Key Drug Interactions
* **Activated Charcoal:** May adsorb acetylcysteine. Administer activated charcoal at least 1–2 hours prior to oral acetylcysteine if indicated for acetaminophen ingestion.
* **Nitroglycerin:** Acetylcysteine may enhance the vasodilatory and antiplatelet effects, potentially causing severe hypotension and headache.
## Monitoring
* **Acetaminophen Overdose:** Serum acetaminophen levels (Rumack-Matthew nomogram), ALT/AST, INR, creatinine, and electrolytes.
* **Mucolytic:** Monitor for respiratory distress and ability to clear secretions.
* **IV Infusion:** Monitor for anaphylactoid reactions (stop infusion, manage symptoms, restart at slower rate if mild).
## Clinical Pearls
* **IV vs. Oral:** IV is generally preferred in the US for acetaminophen overdose due to reduced complications (vomiting preventing oral administration), but local institutional protocols vary.
* **Smell:** Patients receiving oral acetylcysteine often find the sulfur smell intolerable; mixing with soda or juice via a straw can improve palatability.
* **Pre-treatment:** If administering via nebulizer, always co-administer a bronchodilator (e.g., salbutamol) to prevent drug-induced bronchospasm.
* **Standardization:** Ensure accurate weight-based calculations, especially in pediatric populations, to avoid pediatric overdose or administration errors.
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**Disclaimer:** This information is for educational purposes only. Always consult current institutional protocols, package inserts, and evidence-based clinical decision support tools before prescribing or administering medication.
