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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucoproteins, reducing mucus viscosity. It also serves as an antidote for acetaminophen overdose by replenishing glutathione stores. ## Primary Indications * **Acetaminophen Overdose:** Treatment to prevent or reduce liver toxicity. * **Mucolytic:** Adjunct therapy for conditions with excessive, tenacious mucus (e.g., cystic fibrosis, chronic bronchitis, 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:** A second infusion of 50 mg/kg over 16 hours is typically given. The total duration is usually 20-21 hours. * **Alternative Oral Protocol:** 140 mg/kg PO loading dose, followed by 70 mg/kg PO every 4 hours for 17 doses. This may be less effective and associated with more nausea/vomiting. * *Note:* Specific IV infusion rates and concentrations are crucial and often based on local hospital protocols. Dosing may need adjustment based on acetaminophen levels and time since ingestion. * **Mucolytic:** * **Inhaled:** 10% solution: 3-5 mL nebulized every 4-12 hours. 20% solution: 3-5 mL nebulized every 4-12 hours. * **Oral (less common for mucolytic):** 200 mg (600 mg/day) to 400 mg (1200 mg/day) PO divided BID to TID. ## Pediatric Dosing * **Acetaminophen Overdose (IV):** * **Loading Dose:** 150 mg/kg IV infused over 1 hour. * **Second Dose:** 50 mg/kg IV infused over 16 hours. * **Subsequent Doses:** A second infusion of 50 mg/kg over 16 hours is typically given. The total duration is usually 20-21 hours. * *Note:* Dosing is weight-based. For children < 20 kg, initial loading dose concentration should not exceed 300 mg/mL. Subsequent infusions should be diluted to a maximum of 10 mg/mL to avoid fluid overload. Local protocols are essential. * **Mucolytic (Inhaled):** * **Children 2-12 years:** 10% solution: 1-2 mL nebulized every 4-12 hours. 20% solution: 1-2 mL nebulized every 4-12 hours. * **Infants < 2 years:** 10% solution: 1 mL nebulized every 4-12 hours. 20% solution: 1 mL nebulized every 4-12 hours. ## Dose Adjustments * No specific dose adjustments are generally required for renal or hepatic impairment for the acetaminophen overdose protocol, as the goal is to restore glutathione levels systemically. * For mucolytic use, monitor for bronchospasm, especially in asthmatics. ## Contraindications * Known hypersensitivity to acetylcysteine. * Aspiration of vomitus (oral formulation). ## Adverse Effects * **IV:** Anaphylactoid reactions (rash, pruritus, flushing, urticaria, bronchospasm, dyspnea, angioedema), nausea, vomiting, fever. * **Inhaled:** Bronchospasm, stomatitis, nausea, vomiting, rhinorrhea. * **Oral:** Nausea, vomiting, diarrhea, abdominal pain. ## Key Drug Interactions * **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its absorption. Administer acetylcysteine at least 1 hour after activated charcoal. * **Nitroglycerin:** Concurrent use may potentiate the hypotensive effects of nitroglycerin. Monitor blood pressure. ## Monitoring * **Acetaminophen Overdose:** * Acetaminophen plasma levels (initial and serial). * Liver function tests (AST, ALT, bilirubin, INR). * Renal function. * Serum electrolytes. * Clinical signs of liver toxicity. * **Mucolytic:** * Pulmonary status (respiratory rate, oxygen saturation, auscultation). * For bronchospasm, especially in patients with asthma. ## Clinical Pearls * For IV administration in acetaminophen overdose, prompt initiation is critical. The antidote is most effective when given within 8-10 hours of acetaminophen ingestion. * Dilute IV acetylcysteine to reduce the risk of anaphylactoid reactions and phlebitis. A concentration of 10 mg/mL is often recommended for subsequent infusions, but check local protocols. * Premedication with an H1 antagonist (e.g., diphenhydramine) may be considered to mitigate anaphylactoid reactions, though evidence is limited. Bronchodilators should be readily available. * If vomiting occurs with oral acetylcysteine, antiemetics may be necessary. Consider nasogastric administration if vomiting is persistent. * For inhaled use, consider administering a bronchodilator first if the patient has reactive airway disease. *** *Disclaimer: This information is for educational purposes only and does not substitute for professional medical advice. Always consult the most current prescribing information and guidelines, and verify doses with a physician or other qualified healthcare provider.*