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# Acetylcysteine ## Overview Acetylcysteine (N-acetylcysteine, NAC) is an mucolytic agent and an antidote for acetaminophen overdose. It works by replenishing glutathione stores, which are depleted by toxic acetaminophen metabolites. ## Primary Indications * **Acetaminophen Overdose:** Primary indication as an antidote. * **Mucolytic:** To thin and loosen mucus in certain respiratory conditions (e.g., cystic fibrosis, chronic obstructive pulmonary disease). ## Adult Dosing ### Acetaminophen Overdose **Oral:** * **Loading Dose:** 140 mg/kg. * **Maintenance Dose:** 70 mg/kg every 4 hours for 17 doses (total of 72 hours). * Maximum dose for oral administration is typically not specified, but large doses may be required. **Intravenous (IV):** * **Loading Dose:** 150 mg/kg infused over 1 hour. * **Second Infusion:** 50 mg/kg infused over 4 hours. * **Third Infusion:** 100 mg/kg infused over 16 hours. * *Note: Local protocols may vary, especially regarding infusion rates and concentrations.* * Maximum IV dose is typically not specified but is guided by patient weight and duration of therapy. ### Mucolytic **Oral:** * 600 mg to 1800 mg daily, divided into 2 to 3 doses. **Inhaled:** * 3 to 5 mL of a 20% solution or 6 to 10 mL of a 10% solution, nebulized every 2 to 6 hours. ## Pediatric Dosing ### Acetaminophen Overdose Dosing is the same as adult dosing based on weight (140 mg/kg loading, 70 mg/kg maintenance for oral; 150 mg/kg loading, 50 mg/kg, 100 mg/kg for IV). * *Note: IV formulations for pediatric use may require specific dilution and administration protocols.* ### Mucolytic **Oral:** * **Children < 2 years:** 50 mg to 100 mg twice daily. * **Children 2 to 12 years:** 100 mg to 200 mg two to four times daily. * **Children > 12 years:** Same as adult dosing. **Inhaled:** * **Children < 1 year:** 10% solution, 1 mL nebulized every 2 to 6 hours. * **Children > 1 year:** 10% or 20% solution, 3-5 mL nebulized every 2 to 6 hours. ## Dose Adjustments * **Renal Impairment:** No specific dose adjustments are routinely recommended, but caution may be warranted. * **Hepatic Impairment:** No specific dose adjustments are routinely recommended, but caution may be warranted, especially in acetaminophen overdose. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. * *Note: Use with caution in patients with a history of asthma or bronchospasm due to potential for bronchoconstriction with inhaled formulations.* ## Adverse Effects * **IV Acetaminophen Overdose:** Anaphylactoid reactions (rash, urticaria, pruritus, flushing, bronchospasm, angioedema, dyspnea), nausea, vomiting. * **Oral:** Nausea, vomiting, diarrhea, stomatitis. * **Inhaled:** Bronchospasm, bronchoconstriction, wheezing, stomatitis, rhinorrhea, nausea. ## Key Drug Interactions * **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its absorption. Separate administration by at least 1 hour. * **Nitroglycerin:** May potentiate hypotensive effects. ## Monitoring * **Acetaminophen Overdose:** * **Acetaminophen and Glutathione Levels:** Monitor serial acetaminophen levels to assess the need for continued therapy. Glutathione levels are not routinely monitored. * **Liver Function Tests (LFTs):** Monitor for hepatotoxicity, especially in the first 72 hours. * **Renal Function:** Monitor for potential nephrotoxicity. * **Signs of Anaphylactoid Reaction:** Closely monitor vital signs and for signs of allergic reaction during IV infusion. * **Mucolytic:** Monitor respiratory status and sputum production. ## Clinical Pearls * For IV administration in acetaminophen overdose, slow infusion rates initially may reduce the incidence of anaphylactoid reactions. * The smell of acetylcysteine can be unpleasant; this is normal and does not indicate spoilage. * When used as a mucolytic, adequate hydration is important to enhance its effectiveness. *** **Disclaimer:** This information is for educational purposes only and does not constitute medical advice. Always consult the most current prescribing information and professional guidelines for definitive drug management decisions. Verify all dosages and indications with an up-to-date drug reference.