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# Acetylcysteine ## Overview Acetylcysteine (NAC) 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 Agent:** For conditions with thick mucus secretions (e.g., cystic fibrosis, COPD, pneumonia, tracheostomy care). ## Adult Dosing **Acetaminophen Overdose:** * **Loading Dose:** 150 mg/kg IV over 60 minutes. * **Second Dose:** 50 mg/kg IV over 60 minutes, 4 hours after the loading dose. * **Subsequent Doses:** 100 mg/kg IV over 15-60 minutes every 4 hours for a total of 17 doses (or 72 hours). * **Maximum dose:** Protocols may vary; some recommend a maximum of 150 mg/kg per dose or a total daily maximum. Local protocol should be consulted. **Mucolytic Agent (Oral/Nebulized):** * **Oral:** 200 mg (e.g., 1 effervescent tablet) two to three times daily. Higher doses up to 1200 mg/day have been used. * **Nebulized:** 1-10 mL of 10-20% solution every 2-6 hours, as needed. 20% solution: 3-10 mL; 10% solution: 6-10 mL. ## Pediatric Dosing **Acetaminophen Overdose:** * Dosing is weight-based, identical to adult dosing (150 mg/kg IV loading, followed by 50 mg/kg IV, then 100 mg/kg IV q4h for 17 doses). * Ensure accurate weight measurement for appropriate dilution and infusion rates. **Mucolytic Agent (Nebulized):** * **Infants/Children:** 1-2 mL of 20% solution or 2-4 mL of 10% solution every 2-6 hours. ## Dose Adjustments * **Renal Impairment:** No specific dose adjustments are typically required, but caution may be warranted. * **Hepatic Impairment:** No specific dose adjustments are typically required for acetaminophen overdose treatment, as the goal is to support liver function. ## Contraindications * Known hypersensitivity to acetylcysteine. * Active bronchospasm (for nebulized form). ## Adverse Effects * **IV Administration:** Anaphylactoid reactions (rash, pruritus, angioedema, bronchospasm, dyspnea), flushing, hypotension, tachycardia. Nausea and vomiting are common. * **Nebulized Administration:** Bronchospasm, rhinorrhea, nausea, stomatitis. * **Oral Administration:** Nausea, vomiting, diarrhea, rash. ## Key Drug Interactions * **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its absorption. Administer oral acetylcysteine at least 1 hour after activated charcoal. * **Nitroglycerin:** May potentiate nitroglycerin's vasodilatory effects, potentially leading to additive hypotension. ## Monitoring * **Acetaminophen Overdose:** * **Liver Function Tests (LFTs):** ALT, AST, bilirubin, INR, prothrombin time, creatinine, glucose, electrolytes at baseline and then as clinically indicated (e.g., every 12-24 hours). * **Acetaminophen Trough Levels:** Monitor levels to assess efficacy of treatment and guide duration. * **Clinical Signs:** Watch for signs of hepatic encephalopathy or liver failure. * **Mucolytic Use:** * **Pulmonary Function:** Monitor for improved airway clearance and reduction in mucus. * **Bronchospasm:** Assess for any signs or symptoms. ## Clinical Pearls * For IV administration in acetaminophen overdose, meticulous adherence to the protocol is crucial. If the patient vomits the initial dose, it may need to be re-administered. Antiemetics may be considered. * The smell of acetylcysteine is characteristically sulfurous ("rotten eggs"); this is normal and does not indicate spoilage. * Diluting IV acetylcysteine may reduce the risk of anaphylactoid reactions and phlebitis. Common dilutions include 5% or 10%. * Continuous IV infusion of acetylcysteine is generally preferred over bolus administration for acetaminophen overdose to maintain therapeutic plasma concentrations and potentially reduce adverse reactions. *** **Disclaimer:** This information is intended for clinical use and does not replace professional judgment. Always consult the current prescribing information and relevant institutional protocols for definitive guidance.