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# Acetylcysteine ## Overview Acetylcysteine (NAC) is a mucolytic agent that also serves as an antidote for acetaminophen overdose. It works by replenishing glutathione stores, which are depleted during acetaminophen toxicity, and by breaking disulfide bonds in mucus. ## Primary Indications * Acetaminophen overdose * Adjunct therapy for respiratory conditions characterized by thick mucus secretions (e.g., bronchitis, COPD, cystic fibrosis) ## Adult Dosing **Acetaminophen Overdose:** The standard 21-hour IV protocol is typically 300 mg/kg loading dose followed by 100 mg/kg every 4 hours for 17 doses. Maximum dose per infusion is generally not specified but should be guided by clinical response and tolerability. * **Loading Dose:** 150 mg/kg IV over 60 minutes (maximum 15g). * **Maintenance Dose:** 12.5 mg/kg/hour IV for 4 hours, then 6.25 mg/kg/hour IV for 16 hours. * **Oral Alternative:** Often 140 mg/kg PO loading dose, followed by 70 mg/kg PO every 4 hours for 17 doses. **Respiratory Conditions:** * **Inhalation:** 3-5 mL of a 20% solution or 6-10 mL of a 10% solution, nebulized every 2-6 hours, as needed. * **Oral:** 200 mg to 600 mg PO bid-tid. ## Pediatric Dosing **Acetaminophen Overdose:** Dosing is weight-based and follows the same regimen as adults, adjusted for pediatric weight. Local protocols may vary. * **Loading Dose:** 150 mg/kg IV over 60 minutes. * **Maintenance Dose:** 12.5 mg/kg/hour IV for 4 hours, then 6.25 mg/kg/hour IV for 16 hours. Oral dosing is also available and weight-adjusted. **Respiratory Conditions:** * **Inhalation:** 1-2 mL of a 20% solution or 2-4 mL of a 10% solution, nebulized TID-QID. ## Dose Adjustments No specific dose adjustments are typically required for renal or hepatic impairment. However, caution is advised in severe impairment. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. ## Adverse Effects * **IV Administration:** Anaphylactoid reactions (rash, pruritus, angioedema, bronchospasm), nausea, vomiting. Hypotension with rapid infusion. * **Inhalation:** Bronchospasm, increased secretions, stomatitis, nausea, vomiting. * **Oral:** Nausea, vomiting, diarrhea, rash. ## Key Drug Interactions * **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its effectiveness. Separate administration by at least 1 hour. ## Monitoring * **Acetaminophen Overdose:** Serum acetaminophen levels and liver function tests (ALT, AST, bilirubin, INR). Clinical status (mental state, respiratory status, hemodynamic stability). * **Respiratory Conditions:** Respiratory status, sputum volume and consistency. ## Clinical Pearls * For IV administration, slow infusion and pre-treatment with antihistamines may mitigate anaphylactoid reactions. * The smell of acetylcysteine can be unpleasant and may cause nausea. * Ensure adequate hydration when used for respiratory conditions. * The optimal antidote protocol, especially for prolonged ingestions or delayed presentations of acetaminophen overdose, may be guided by local institutional protocols. *** *Disclaimer: This information is intended for educational purposes and does not substitute professional medical advice. Always consult the most current prescribing information and your healthcare provider for any medical decisions.*