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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent and an antidote for acetaminophen overdose. It works by breaking disulfide bonds in mucoproteins, decreasing mucus viscosity, and by replenishing hepatic glutathione stores. ## Primary Indications * Acetaminophen overdose * Adjunct therapy in patients with a lung disease such as chronic obstructive pulmonary disease (COPD), bronchitis, or cystic fibrosis to help loosen mucus secretions. ## Adult Dosing **Acetaminophen Overdose:** * **IV Administration:** Typically a 3-bag, 72-hour regimen. * **Loading Dose:** 150 mg/kg IV over 1 hour. * **Second Infusion:** 50 mg/kg IV over the next 1 hour (maximum 6.25 g/hr). * **Third Infusion:** 100 mg/kg IV over the next 16 hours (maximum 12.5 g/hr). * *Note: Specific concentrations and infusion rates vary based on protocol and product availability. Consult local protocol.* * **Oral Administration:** Typically a 3-bag, 72-hour regimen. * **Loading Dose:** 140 mg/kg PO. * **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses. * Dilute in 5% dextrose or fruit juice to improve palatability. **Mucolytic:** * **Nebulized:** 20% solution: 1-10 mL once to several times daily. 10% solution: 2-10 mL once to several times daily. * **Oral:** 200 mg twice daily to 1000 mg twice daily. ## Pediatric Dosing **Acetaminophen Overdose:** * **IV Administration:** Dosing is the same as adults (150 mg/kg loading, then 50 mg/kg, then 100 mg/kg). Due to the risk of anaphylactoid reactions, slow infusion rate in children if higher concentrations are used, or consider diluting further. * **Oral Administration:** Dosing is the same as adults (140 mg/kg loading, then 70 mg/kg PO every 4 hours for 17 doses). **Mucolytic:** * **Nebulized:** * **< 1 year:** 1-2 mL of 20% solution or 2-4 mL of 10% solution every 2-6 hours. * **1-12 years:** 2-10 mL of 20% solution or 4-10 mL of 10% solution every 2-6 hours. * **> 12 years:** Same as adult dosing. * **Oral:** Dosing is less established and varies. Commonly used doses range from 100 mg to 200 mg twice daily in younger children, up to adult doses in older children and adolescents. ## Dose Adjustments No dose adjustments are typically required for hepatic or renal impairment for the antidote indication. For mucolytic use, doses may be adjusted based on patient response and tolerance. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. * Active hemorrhage (relative contraindication for nebulized use if significant hemoptysis). ## Adverse Effects * **IV (Overdose):** Anaphylactoid reactions (rash, pruritus, bronchospasm, angioedema, hypotension) are common and typically related to infusion rate. Nausea and vomiting. * **Nebulized:** Bronchospasm, stomatitis, rhinorrhea, nausea. * **Oral:** Nausea, vomiting, diarrhea, abdominal pain. ## Key Drug Interactions * **Activated Charcoal:** Decreases absorption of oral acetylcysteine. If both are used, administer charcoal first and then acetylcysteine 1 hour later. * **Nitroglycerin:** May potentiate hypotensive effects. ## Monitoring * **Acetaminophen Overdose:** * Liver function tests (ALT, AST, bilirubin, INR). * Renal function. * Serum acetaminophen levels. * Monitor for signs of anaphylactoid reaction (vital signs, respiratory status). * **Mucolytic Use:** * Respiratory status, sputum production, and viscosity. * Monitor for bronchospasm. ## Clinical Pearls * For IV acetylcysteine in acetaminophen overdose, the antidote effect is most pronounced when initiated within 8-10 hours of ingestion. However, it should be given regardless of time elapsed if acetaminophen levels are in the treatment nomogram range or if level is unavailable. * Anaphylactoid reactions are common but usually manageable by slowing the infusion rate. Antihistamines may be used for prophylaxis or treatment. * Oral acetylcysteine may be an alternative if IV access is difficult or if IV product is unavailable, but it has a higher incidence of nausea and vomiting. * Nebulized acetylcysteine can sometimes worsen bronchospasm; co-administration with a bronchodilator is often recommended. *** **Disclaimer:** This information is intended for educational purposes only and does not constitute medical advice. Always consult the most current prescribing information, guidelines, and institutional protocols before making clinical decisions.