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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent that also serves as an antidote for acetaminophen overdose. It works by replenishing glutathione stores, which are depleted during acetaminophen metabolism, and by directly binding to the toxic metabolite of acetaminophen. ## Primary Indications * **Acetaminophen Overdose:** Treatment to prevent or reduce liver damage. * **Mucolytic Agent:** To thin and loosen mucus in conditions such as chronic bronchitis, emphysema, and cystic fibrosis. ## Adult Dosing ### Acetaminophen Overdose (Oral or Intravenous) * **Loading Dose:** 140 mg/kg orally or intravenously. * **Maintenance Dose:** 70 mg/kg orally or intravenously every 4 hours for 17 doses. * **Maximum Dose:** Not typically limited by total daily dose but by individual dose size based on body weight. * **Note:** Dosing protocols may vary slightly by institution. Intravenous administration may require dilution; consult specific product labeling for preparation instructions. ### Mucolytic Agent * **Oral:** 200 mg to 400 mg (typically available as 200 mg, 600 mg, or 1200 mg effervescent tablets or granules) two to three times daily. * **Intravenous:** Not a standard route for mucolytic therapy. * **Nebulization:** 10% solution: 3-5 mL every 3-4 hours. 20% solution: 1-2 mL every 3-4 hours. * **Direct Instillation:** 10% solution: 1-2 mL into tracheostomy tube every 1-4 hours. ## Pediatric Dosing ### Acetaminophen Overdose (Oral or Intravenous) * **Loading Dose:** 140 mg/kg orally or intravenously. * **Maintenance Dose:** 70 mg/kg orally or intravenously every 4 hours for 17 doses. * **Note:** Protocols are generally consistent with adult dosing based on weight. Intravenous administration may require different dilution and infusion rates for pediatric patients. ### Mucolytic Agent (Nebulization) * **Nebulization (10% solution):** 1-2 mL every 3-4 hours. * **Nebulization (20% solution):** 1 mL every 3-4 hours. ## Dose Adjustments * **Renal Impairment:** No specific dose adjustments are routinely recommended, but caution may be warranted in severe impairment. * **Hepatic Impairment:** No specific dose adjustments are routinely recommended for acetaminophen overdose, as the antidote is crucial even in the presence of liver disease. For mucolytic use, observe for potential increased adverse effects. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. * Active peptic ulcer disease (oral formulations may exacerbate). ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, stomatitis, rash, pruritus, fever, rhinorrhea, bronchospasm (especially with nebulized solutions). * **Serious:** Anaphylactoid reactions (can be severe with IV administration), angioedema. ## Key Drug Interactions * **Activated Charcoal:** May adsorb acetylcysteine if given orally, reducing its absorption and efficacy in acetaminophen overdose. Separate administration by at least 1 hour. * **Nitroglycerin:** May potentiate the hypotensive effect of nitroglycerin. Monitor blood pressure. ## Monitoring * **Acetaminophen Overdose:** * Serum acetaminophen levels (serial measurements are crucial to assess risk and duration of therapy). * Liver function tests (AST, ALT, bilirubin, PT/INR) starting at 24 hours after overdose and continuing as clinically indicated. * Renal function and electrolytes. * **Mucolytic Use:** * Respiratory status, mucus expectoration. * Bronchospasm. ## Clinical Pearls * For acetaminophen overdose, the timing of acetylcysteine initiation is critical. Treatment should be started immediately if an overdose is suspected, even before acetaminophen levels are available. * The Rumack-Matthew nomogram is a guide for treatment decisions based on acetaminophen levels and time since ingestion. * Intravenous acetylcysteine administration can be associated with anaphylactoid reactions. Facilities should have protocols for managing these reactions, including slow infusion rates, premedication (e.g., with diphenhydramine), and availability of emergency support. * Nebulized acetylcysteine has a characteristic unpleasant odor, which may limit patient compliance. *** *This information is intended for clinical pharmacists and healthcare professionals. It is not a substitute for professional medical advice. Always verify current prescribing information and institutional protocols before administering any medication.*