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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucoproteins, reducing mucus viscosity. It also acts as an antidote for acetaminophen overdose by replenishing hepatic glutathione stores. ## Primary Indications * **Acetaminophen Overdose:** To prevent or treat acetaminophen-induced hepatotoxicity. * **Mucolytic:** To thin mucus in respiratory conditions such as cystic fibrosis, COPD, and pneumonia. ## Adult Dosing **Acetaminophen Overdose:** * **Loading Dose:** 150 mg/kg IV infused over 1 hour. * **Second Dose:** 50 mg/kg IV infused over 16 hours. * **Subsequent Doses:** 50 mg/kg IV infused over 16 hours for a total of 72 hours (usually 16-20 doses). * *Note:* Dosing may vary based on initial acetaminophen levels and time since ingestion. Alternative protocols exist. Oral administration is also an option, particularly for milder ingestions or when IV access is limited. Oral loading dose is typically 140 mg/kg followed by 70 mg/kg every 4 hours for 17 doses. **Mucolytic:** * **Nebulized:** 10% solution: 3-5 mL q3-4h PRN. 20% solution: 6-10 mL q3-4h PRN. * **Oral:** 200 mg (e.g., 2 standard effervescent tablets) PO BID-TID. 600 mg PO once daily. * **Intravenous:** Typically reserved for acetaminophen overdose; not standard for mucolytic use. ## Pediatric Dosing **Acetaminophen Overdose:** * **Loading Dose:** 150 mg/kg IV infused over 1 hour. * **Second Dose:** 50 mg/kg IV infused over 16 hours. * **Subsequent Doses:** 50 mg/kg IV infused over 16 hours for a total of 72 hours. * *Note:* Use weight-based calculations carefully. Oral dosing is also an option, as described in adult dosing. **Mucolytic:** * **Nebulized:** * <1 year: 10% solution: 1-2 mL q2-6h PRN. * >1 year: 10% solution: 3-5 mL q3-4h PRN. Or 20% solution: 6-10 mL q3-4h PRN. * **Oral:** * 1-2 years: 100 mg PO BID. * >2 years: 200 mg PO BID-TID. ## Dose Adjustments * **Renal Impairment:** No specific dose adjustment for IV acetylcysteine in overdose. Use with caution in severe renal impairment for mucolytic indications. * **Hepatic Impairment:** No specific dose adjustment for IV acetylcysteine in overdose, as its purpose is to replete glutathione. ## Contraindications * Hypersensitivity to acetylcysteine. * Severe bronchospasm with nebulized formulation (rare). ## Adverse Effects * **IV (Overdose):** Anaphylactoid reactions (rash, pruritus, urticaria, bronchospasm, angioedema), flushing, hypotension, tachycardia. Nausea and vomiting are common. * **Nebulized:** Bronchospasm, rhinorrhea, nausea, vomiting, stomatitis. * **Oral:** Nausea, vomiting, diarrhea, stomatitis. ## Key Drug Interactions * **Activated Charcoal:** May adsorb acetylcysteine, reducing its efficacy in acetaminophen overdose if given concurrently. Separate administration. * **Nitroglycerin:** IV acetylcysteine may potentiate the hypotensive effect of nitroglycerin. Monitor blood pressure. ## Monitoring * **Acetaminophen Overdose:** * Acetaminophen levels (at appropriate intervals). * Liver function tests (AST, ALT, bilirubin, INR). * Renal function. * Signs of anaphylactoid reaction. * **Mucolytic:** * Respiratory status, sputum production and viscosity. * Bronchospasm. ## Clinical Pearls * The odor of acetylcysteine is unpleasant (sulfur-like) and may cause nausea or vomiting, especially with oral or nebulized formulations. Antiemetics may be helpful. * For IV use in acetaminophen overdose, ensure adequate hydration and monitor closely for anaphylactoid reactions, which can occur even with appropriate dosing. Epinephrine may be needed for severe reactions. * Oral acetylcysteine is generally less effective than IV for acetaminophen overdose but may be considered if IV access is difficult or for less severe ingestions. * Nebulized acetylcysteine can worsen bronchospasm in some patients. Co-administration with a bronchodilator is often recommended. *** **Disclaimer:** This information is intended for educational purposes only and does not substitute for professional medical advice. Always verify current prescribing information with the official drug manufacturer's labeling and consult with a healthcare professional before making any treatment decisions.