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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucus, decreasing its viscosity. It is also an antidote for acetaminophen overdose by replenishing glutathione stores. ## Primary Indications * **Acetaminophen overdose:** To prevent or reduce liver toxicity. * **Mucolytic:** To thin respiratory secretions in conditions like COPD, cystic fibrosis, and pneumonia. ## Adult Dosing * **Acetaminophen Overdose:** * **Loading dose:** 150 mg/kg IV infused over 60 minutes. * **Second dose:** 50 mg/kg IV infused over 60 minutes 4 hours after the loading dose. * **Subsequent doses:** 100 mg/kg IV infused over 16 hours (total infusion time 17 hours, including loading and second dose). * **Alternative oral protocol:** 140 mg/kg PO loading dose, followed by 70 mg/kg PO every 4 hours for 17 doses. * *Note:* Dosing may be adjusted based on acetaminophen levels and time since ingestion. Local protocols should be consulted. * **Mucolytic:** * **Inhaled:** 3 mL to 5 mL of 10% or 20% solution via nebulizer every 4 to 12 hours. * **Intranasal:** 1-2 drops of 10% solution into each nostril every 1-2 hours. (Less common). ## Pediatric Dosing * **Acetaminophen Overdose:** Dosing is the same as adults (150 mg/kg IV loading dose, followed by 50 mg/kg IV 4 hours later, then 100 mg/kg IV over 16 hours). * **Mucolytic:** * **Inhaled:** 1 mL to 2 mL of 10% or 20% solution via nebulizer every 4 to 12 hours. ## Dose Adjustments No specific dose adjustments are typically required for renal or hepatic impairment for the antidote indication, but caution is advised due to potential accumulation. For mucolytic use, adjust frequency based on patient response and tolerance. ## Contraindications * Hypersensitivity to acetylcysteine. * *Oral administration:* High risk of aspiration or vomiting. * *IV administration:* Avoid in patients with known severe bronchospasm or airway disease where bronchoconstriction may be exacerbated. ## Adverse Effects * **IV:** Anaphylactoid reactions (rash, pruritus, urticaria, bronchospasm, angioedema, hypotension), flushing, fever, headache. * **Inhaled:** Bronchospasm, nausea, vomiting, stomatitis, rhinorrhea. * **Oral:** Nausea, vomiting, diarrhea. ## Key Drug Interactions * **Activated Charcoal:** May adsorb acetylcysteine when used for acetaminophen overdose. Administer acetylcysteine at least 1 hour after activated charcoal. * **Nitroglycerin:** Concurrent use may lead to increased hypotension. ## Monitoring * **Acetaminophen Overdose:** Serum acetaminophen levels, liver function tests (ALT, AST, bilirubin), coagulation profile (PT/INR), renal function, glucose. Clinical signs of liver toxicity. * **Mucolytic:** Respiratory status, mucus production, presence of bronchospasm. ## Clinical Pearls * For IV administration in acetaminophen overdose, the loading dose should be infused over 60 minutes. Rapid infusion can cause anaphylactoid reactions. * If bronchospasm occurs during inhaled administration, discontinue and consider a bronchodilator. * The smell of acetylcysteine is often described as "rotten eggs" and can be unpleasant. *** **Disclaimer:** This information is intended for educational purposes only and does not constitute medical advice. Always consult the most current prescribing information, local protocols, and a qualified healthcare provider for any treatment decisions.