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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent that works by breaking disulfide bonds in mucus, reducing its viscosity. It is also an antidote for acetaminophen overdose. ## Primary Indications * **Acetaminophen Overdose:** Treatment to prevent or reduce liver damage. * **Mucolytic:** To thin mucus in conditions like 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:** An additional 150 mg/kg IV infused over 16 hours may be given if serum acetaminophen levels are still toxic after the initial 20-hour infusion. * **Oral Protocol:** Can also be given orally, with initial doses of 140 mg/kg followed by 70 mg/kg every 4 hours for 17 doses. **Mucolytic:** * **Inhalation:** 1 to 10 mL of a 10% or 20% solution nebulized every 2 to 6 hours. * **Intranasal:** 1-2 drops of a 10% solution instilled into each nostril every 1-2 hours. (Less common). * **Oral:** 600 mg once daily or 200 mg three times daily. ## Pediatric Dosing **Acetaminophen Overdose:** * Dosing is the same as adults (150 mg/kg IV loading dose, followed by 50 mg/kg IV over 16 hours). Concentration should be adjusted based on patient weight to avoid fluid overload, especially in neonates. **Mucolytic:** * **Inhalation:** 1 to 10 mL of a 10% or 20% solution nebulized every 2 to 6 hours. Weight-based dosing can be used for younger children, but often a standard volume is used. ## Dose Adjustments * No specific dose adjustments are typically needed for renal or hepatic impairment for the mucolytic indication. * For acetaminophen overdose, dose adjustments are not routinely made for renal or hepatic impairment; however, careful monitoring is essential. ## Contraindications * Hypersensitivity to acetylcysteine. ## Adverse Effects * **Common (Inhaled):** Bronchospasm, rhinorrhea, nausea, vomiting, stomatitis. * **Common (IV for Overdose):** Anaphylactoid reactions (rash, urticaria, pruritus, angioedema, bronchospasm), nausea, vomiting. ## Key Drug Interactions * **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its efficacy in acetaminophen overdose. Separate administration by at least 1 hour. ## Monitoring * **Acetaminophen Overdose:** * Serum acetaminophen levels at appropriate time points. * Liver function tests (AST, ALT, bilirubin, INR). * Renal function. * Glucose levels (if receiving IV dextrose). * **Mucolytic:** * Respiratory status, effectiveness of mucus clearance. * Signs of bronchospasm. ## Clinical Pearls * The odor of acetylcysteine is often described as unpleasant (sulfurous) and can be a deterrent for patients. * For IV administration in acetaminophen overdose, ensure adequate hydration and monitor for anaphylactoid reactions, which can occur even with the first dose. Promptly treat bronchospasm if it occurs. * Oral acetylcysteine may cause nausea and vomiting, especially at higher doses. Antiemetics may be considered. * The efficacy of acetylcysteine in acetaminophen overdose is most pronounced when initiated within 8-10 hours of ingestion, but it should still be administered even if presentation is later, as it can provide benefit. Please verify current prescribing information with the manufacturer's package insert or reliable drug compendia before initiating treatment.