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# Acetylcysteine ## Overview Acetylcysteine (N-acetylcysteine, NAC) is a mucolytic agent and an antidote for acetaminophen overdose. It is available in oral and intravenous formulations. ## Primary Indications * **Acetaminophen Overdose:** Treatment of acetaminophen toxicity. * **Mucolytic:** Liquefaction of viscous mucus secretions in respiratory conditions such as bronchitis, cystic fibrosis, and emphysema. ## Adult Dosing ### Acetaminophen Overdose * **Oral:** Typically a 3-bag regimen over 72 hours: * **Loading Dose:** 140 mg/kg orally, administered as a 5% solution (e.g., 140 mg/mL). * **Maintenance Dose:** 70 mg/kg orally every 4 hours for 17 doses. * Maximum single dose: 2000 mg. * **Intravenous:** Protocols vary. A common regimen involves: * **Loading Dose:** 150 mg/kg IV over 1 hour. * **Second Dose:** 50 mg/kg IV over the next 4 hours. * **Third Dose:** 100 mg/kg IV over the next 16 hours. * Maximum infusion rates and total doses are protocol-dependent and should be adhered to closely. * **Uncertainty:** Optimal IV formulation and protocol may vary; consult local institutional guidelines or poison control. ### Mucolytic * **Oral:** 200 mg to 400 mg twice daily. * **Nebulized:** 1 to 10 mL of a 10% or 20% solution (100 mg/mL or 200 mg/mL) every 2-6 hours as needed. Higher concentrations may be more effective but can cause bronchospasm. May be mixed with a bronchodilator. ## Pediatric Dosing ### Acetaminophen Overdose * **Oral:** Same as adult dosing (140 mg/kg loading dose, then 70 mg/kg every 4 hours for 17 doses). * **Intravenous:** Same as adult dosing, but dose adjustments may be needed based on body weight and specific protocol. * **Uncertainty:** IV dosing protocols for pediatric patients can vary significantly. Consult local guidelines or poison control. ### Mucolytic * **Nebulized:** 1 mL to 5 mL of a 10% or 20% solution (100 mg/mL or 200 mg/mL) every 2-6 hours. ## Dose Adjustments No specific dose adjustments are typically required for renal or hepatic impairment when used for acetaminophen overdose. Dose adjustments are not generally needed for mucolytic therapy, but the lowest effective dose should be used. ## Contraindications * Hypersensitivity to acetylcysteine. ## Adverse Effects * **Anaphylactoid reactions:** Especially with IV administration (rash, urticaria, pruritus, angioedema, bronchospasm, dyspnea). * **Gastrointestinal:** Nausea, vomiting, diarrhea, abdominal pain (more common with oral administration). * **Respiratory:** Bronchospasm, increased secretions (particularly with nebulized use, especially in reactive airway disease). * **Other:** Fever, headache, rhinorrhea. ## Key Drug Interactions * **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its efficacy. If both are used, separate administration times. * **Nitroglycerin:** Potential for additive hypotensive effects. ## Monitoring * **Acetaminophen Overdose:** * **Serum Acetaminophen Levels:** Crucial for guiding treatment duration. * **Liver Function Tests (LFTs):** Monitor for hepatotoxicity. * **Prothrombin Time (PT)/International Normalized Ratio (INR):** Assess for coagulopathy. * **Renal Function:** Monitor for potential nephrotoxicity. * **Clinical Signs and Symptoms:** Observe for signs of acetaminophen toxicity (nausea, vomiting, abdominal pain, jaundice, encephalopathy). * **Mucolytic:** * **Pulmonary Function:** Assess for effectiveness and signs of bronchospasm. * **Sputum Viscosity and Volume:** Monitor for changes. ## Clinical Pearls * For acetaminophen overdose, the antidote effect is greatest when initiated within 8-10 hours of ingestion. However, treatment should be continued even if initiated later, especially if liver injury is present. * Dilute oral acetylcysteine to improve palatability and reduce emesis. A 5% solution is typically used. * Nebulized acetylcysteine can induce bronchospasm. Co-administration with a bronchodilator may be beneficial. * Intravenous acetylcysteine infusion rates and concentrations must be carefully managed to minimize the risk of anaphylactoid reactions. *** **Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before administering any medication.