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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucoproteins, reducing mucus viscosity. It also acts as an antidote for acetaminophen overdose by replenishing hepatic glutathione stores. ## Primary Indications * **Acetaminophen Overdose:** Treatment to prevent or reduce liver injury. * **Mucolytic Agent:** To thin thick mucus secretions in respiratory conditions (e.g., cystic fibrosis, COPD, pneumonia). ## Adult Dosing ### Acetaminophen Overdose * **Intravenous (IV):** * **Loading Dose:** 150 mg/kg IV over 1 hour. * **Second Infusion:** 50 mg/kg IV over 16 hours. * **Third Infusion:** 100 mg/kg IV over 16 hours (total duration 20 hours). * **Maximum Total Dose:** Not to exceed 300 mg/kg for the entire treatment course. * **Oral:** * **Loading Dose:** 140 mg/kg PO. * **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses (total 18 doses). * **Maximum Dose:** 140 mg/kg per dose for loading, 70 mg/kg per dose thereafter. ### Mucolytic Agent * **Nebulized:** 10% solution: 6 mL TID; or 20% solution: 3-5 mL TID. * **Oral:** 200 mg PO BID to TID. Higher doses (e.g., up to 1200 mg/day) may be used in specific conditions like cystic fibrosis, often guided by institutional protocols. ## Pediatric Dosing ### Acetaminophen Overdose * **Intravenous (IV):** Same as adult dosing (150 mg/kg over 1 hour, then 50 mg/kg over 16 hours, then 100 mg/kg over 16 hours). Dose calculated based on weight. * **Oral:** Same as adult dosing (140 mg/kg PO loading, then 70 mg/kg PO every 4 hours for 17 doses). ### Mucolytic Agent * **Nebulized:** * Premature infants and infants: 10% solution 1-2 mL q4-6h; 20% solution 1-2 mL q4-6h. * Children: 10% solution 3-5 mL TID; 20% solution 3 mL TID. * **Oral:** Typically 600 mg/day divided into 2 or 3 doses for children over 14 years. Dosing for younger children is less established and may vary. ## Dose Adjustments * **Renal Impairment:** No specific dose adjustment is typically recommended, but caution is advised. * **Hepatic Impairment:** No specific dose adjustment is typically recommended for overdose treatment, but monitoring is crucial. ## Contraindications * Known hypersensitivity to acetylcysteine or its components. * Active gastric ulcer disease (for oral administration). ## Adverse Effects * **Nebulized:** Bronchospasm (especially in asthmatics), stomatitis, nausea, vomiting, rhinorrhea. * **Intravenous (for overdose):** Anaphylactoid reactions (rash, pruritus, urticaria, angioedema, bronchospasm, dyspnea, hypotension) are the most serious, typically occurring during the initial loading dose. Nausea and vomiting are common. * **Oral:** Nausea, vomiting, diarrhea, rash. ## Key Drug Interactions * **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its absorption. Separate administration by at least 1 hour. * **Nitroglycerin:** Potentiated hypotensive effect. ## Monitoring * **Acetaminophen Overdose:** * Serum acetaminophen levels and nomogram at appropriate time points. * Liver function tests (AST, ALT, bilirubin, PT/INR) every 12-24 hours. * Renal function and electrolytes. * Clinical signs of liver injury. * Monitor for anaphylactoid reactions during IV infusion. * **Mucolytic Agent:** * Pulmonary function tests. * Sputum viscosity and clearance. * Monitor for bronchospasm. ## Clinical Pearls * For IV acetaminophen overdose, prompt