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# Acetylcysteine ## Overview Acetylcysteine (NAC) is a mucolytic agent that decreases the viscosity of respiratory tract secretions. It also serves as an antidote for acetaminophen overdose. ## Primary Indications * **Acetaminophen Overdose:** To prevent or reduce liver toxicity. * **Mucolytic Agent:** To thin and loosen mucus in individuals with conditions such as cystic fibrosis, chronic bronchitis, or pneumonia. ## Adult Dosing * **Acetaminophen Overdose:** * **Initial Loading Dose:** 150 mg/kg intravenously (IV) over 1 hour. * **Second Dose:** 50 mg/kg IV over 1 hour (following the initial dose). * **Subsequent Doses:** 100 mg/kg IV over 16 hours (continuous infusion). * **Maximum Dosing:** Total daily dose depends on the calculation of acetaminophen ingested and the duration of treatment. Initial loading dose should not exceed 150 mg/kg. * **Oral Dosing:** An alternative oral regimen exists, typically 140 mg/kg loading dose followed by 70 mg/kg every 4 hours for 17 doses. Nausea and vomiting are common with oral administration. * **Mucolytic Agent:** * **Nebulized:** 1-2 mL of 20% solution (200-400 mg) or 2-4 mL of 10% solution (200-400 mg) every 2-6 hours. The frequency and concentration may be adjusted based on protocol and patient response. * **Intranasal/Intratracheal:** 1-2 mL of 20% solution (200-400 mg) instilled every 1-4 hours. * **Oral:** 200 mg twice daily to 600 mg three times daily. ## Pediatric Dosing * **Acetaminophen Overdose:** Dosing is weight-based, as outlined in the adult section (150 mg/kg IV loading, then 50 mg/kg IV, then 100 mg/kg IV over 16 hours). Specific concentrations for IV administration in pediatric patients should be calculated to avoid fluid overload. * **Mucolytic Agent:** * **Nebulized:** * **< 1 year:** 1 mL of 10% solution (100 mg) every 2-6 hours. * **1-2 years:** 2 mL of 10% solution (200 mg) every 2-6 hours. * **2-12 years:** 3-5 mL of 10% solution (300-500 mg) or 1-2 mL of 20% solution (200-400 mg) every 2-6 hours. * **> 12 years:** Same as adult dosing. ## Dose Adjustments * **Renal Impairment:** No specific dose adjustment recommendations, but caution is advised. * **Hepatic Impairment:** No specific dose adjustment recommendations for mucolytic use. For acetaminophen overdose, hepatic function is the target of treatment, and NAC administration should be continued based on the antidote protocol. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. ## Adverse Effects * **Common:** Nausea, vomiting, stomatitis, rhinorrhea. * **Less Common:** Bronchospasm (especially with nebulized use), urticaria, pruritus, rash, fever, chills. * **Rare/Serious:** Anaphylactoid reactions (can be severe, particularly with rapid IV infusion). Bronchospasm may be managed with bronchodilators. ## Key Drug Interactions * **Activated Charcoal:** May bind acetylcysteine and reduce its absorption when administered orally for acetaminophen overdose. Separate administration if possible. * **Nitroglycerin:** May potentiate the effects of nitroglycerin, leading to hypotension. ## Monitoring * **Acetaminophen Overdose:** Liver function tests (AST, ALT, bilirubin, INR), serum creatinine, glucose, and electrolytes. Monitor acetaminophen levels. * **Mucolytic Use:** Respiratory status, pulmonary function, and frequency/severity of exacerbations. ## Clinical Pearls * The smell of acetylcysteine can be unpleasant; however, it is not an indicator of product degradation. * For nebulized administration, pre-treatment with a bronchodilator may be considered to reduce the risk of bronchospasm. * IV acetylcysteine for acetaminophen overdose can cause anaphylactoid reactions. Dilution of the IV solution is often recommended to reduce the risk of non-immunologic histamine release and infusion reactions. The optimal dilution and infusion rate can vary by institution and should be followed. * For oral administration in acetaminophen overdose, antiemetics may be necessary due to high rates of nausea and vomiting. *** *Disclaimer: This information is intended for clinical professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant guidelines before administering any medication. Local protocols may supersede general recommendations.*