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# Acetylcysteine ## Overview Acetylcysteine (NAC) is an antidote for acetaminophen overdose and a mucolytic agent. It is available in oral and intravenous formulations. ## Primary Indications * **Acetaminophen overdose:** To prevent or reduce liver toxicity. * **Mucolytic:** To thin respiratory secretions in conditions such as bronchitis, cystic fibrosis, and pneumonia. ## Adult Dosing * **Acetaminophen overdose:** * **Loading dose:** 150 mg/kg intravenously (IV) over 1 hour. * **Second infusion:** 50 mg/kg IV over the next 4 hours. * **Third infusion:** 100 mg/kg IV over the subsequent 16 hours. * **Total daily dose:** Up to 300 mg/kg. * *Alternatively, oral dosing may be used, with specific protocols varying.* * **Mucolytic:** * **Inhalation:** 1 to 10 mL of a 10% or 20% solution every 2 to 6 hours as needed. * **Oral:** 200 mg to 400 mg two to four times daily. ## Pediatric Dosing * **Acetaminophen overdose:** Dosing is weight-based and follows the same protocol as adults (150 mg/kg IV loading dose, followed by 50 mg/kg IV, then 100 mg/kg IV). Maximum doses should not be exceeded. * **Mucolytic:** * **Inhalation:** 1 mL to 3 mL of a 10% or 20% solution every 2 to 6 hours as needed. ## Dose Adjustments * **Renal/Hepatic Impairment:** No specific dose adjustments are typically required for routine mucolytic use. For acetaminophen overdose, close monitoring is essential, and extended treatment may be necessary in severe hepatic dysfunction. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. ## Adverse Effects * **IV administration:** Anaphylactoid reactions (rash, pruritus, bronchospasm, angioedema), flushing, nausea, vomiting, and rarely, hypotension. * **Inhalation:** Bronchospasm, rhinorrhea, nausea, vomiting. * **Oral:** Nausea, vomiting, stomatitis, gastrointestinal upset. ## Key Drug Interactions * **Activated charcoal:** May reduce the absorption of orally administered acetylcysteine. * **Nitroglycerin:** Potential for additive hypotensive effects. ## Monitoring * **Acetaminophen overdose:** Liver function tests (ALT, AST, bilirubin), prothrombin time, INR, creatinine, glucose, and serum acetaminophen levels. Monitor for signs of anaphylactoid reaction. * **Mucolytic:** Respiratory status, sputum production, and signs of bronchospasm. ## Clinical Pearls * For IV acetylcysteine in acetaminophen overdose, the infusion rate should be carefully controlled to minimize anaphylactoid reactions. * Antihistamines may be administered prophylactically to reduce the incidence of anaphylactoid reactions. * Oral acetylcysteine may be associated with a more pronounced gastrointestinal upset. --- **Disclaimer:** This information is intended for healthcare professionals. Always consult the most current prescribing information and institutional protocols before administering any medication.