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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent that breaks down disulfide bonds in mucus, reducing its viscosity. It also acts as an antidote for acetaminophen overdose by replenishing hepatic glutathione stores. ## Primary Indications * **Acetaminophen Overdose:** Treatment to prevent or reduce liver injury. * **Mucolytic:** Adjunct treatment for conditions with thick, tenacious mucus secretions (e.g., chronic bronchitis, emphysema, cystic fibrosis, pneumonia). ## Adult Dosing **Acetaminophen Overdose:** * **Intravenous (IV):** * **Loading Dose:** 150 mg/kg infused over 1 hour. * **Second Dose:** 50 mg/kg infused over 1 hour (typically 4 hours after loading dose). * **Subsequent Doses:** 100 mg/kg infused over 16 hours (total infusion time 21 hours). * *Note:* Maximum dose depends on the specific protocol; some protocols recommend a maximum of 150 mg/kg/hr for the loading dose if patient tolerates. Doses are often calculated based on ideal body weight. * **Oral (PO):** Less common due to gastrointestinal intolerance and slower absorption. * **Loading Dose:** 140 mg/kg. * **Subsequent Doses:** 70 mg/kg every 4 hours for 17 doses (total 72 hours). **Mucolytic:** * **Inhaled (Nebulization):** 3-5 mL of 20% solution or 6-10 mL of 10% solution every 2-6 hours as needed. * **Oral (PO):** 200 mg twice daily or 200 mg three times daily. For cystic fibrosis, up to 800 mg daily may be used. ## Pediatric Dosing **Acetaminophen Overdose:** * Dosing is the same as adult dosing (150 mg/kg IV loading, followed by 50 mg/kg IV, then 100 mg/kg IV over 16 hours). * Dosing is often calculated based on ideal body weight. **Mucolytic:** * **Inhaled (Nebulization):** * **< 4 years:** 1-2 mL of 20% solution or 2-4 mL of 10% solution every 2-6 hours. * **> 4 years:** 3-5 mL of 20% solution or 6-10 mL of 10% solution every 2-6 hours. ## Dose Adjustments No specific dose adjustments are routinely recommended for hepatic or renal impairment for the antidote indication, although caution is advised. For mucolytic use, adjustments are typically based on clinical response and tolerance. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. * Consider caution in patients with active bronchospasm. ## Adverse Effects * **IV (Antidote):** Anaphylactoid reactions (rash, urticaria, bronchospasm, angioedema, hypotension), flushing, nausea, vomiting. Premedication with an H1 and/or H2 antagonist may be considered. * **Inhaled:** Bronchospasm, nausea, vomiting, stomatitis, rhinorrhea. * **Oral:** Nausea, vomiting, diarrhea, rash. ## Key Drug Interactions * **Activated Charcoal:** May adsorb oral acetylcysteine, reducing its efficacy in acetaminophen overdose. If both are indicated, administer acetylcysteine first, then activated charcoal if necessary, or separate administration by at least 1 hour. * **Nitroglycerin:** Potential for additive hypotension and vasodilation. Monitor blood pressure closely. ## Monitoring * **Acetaminophen Overdose:** * Acetaminophen and salicylate levels (to assess toxicity and guide therapy duration). * Liver function tests (LFTs) (AST, ALT, bilirubin, INR) to assess for hepatic injury. * Renal function. * Glucose levels. * Vital signs, especially during IV infusion, for anaphylactoid reactions. * **Mucolytic:** * Pulmonary status, mucus production, and patient's ability to clear secretions. * Bronchospasm, especially with inhaled formulations. ## Clinical Pearls * The IV formulation for acetaminophen overdose is the preferred route due to better absorption and reduced gastrointestinal side effects compared to oral. * Anaphylactoid reactions are common with IV acetylcysteine and are often not true IgE-mediated allergies but rather dose- or rate-dependent histamine release. Slowing the infusion rate can often manage symptoms. * For inhaled acetylcysteine, consider co-administration with a bronchodilator to mitigate bronchospasm. * The duration of IV acetylcysteine therapy for acetaminophen overdose is typically guided by acetaminophen levels and LFTs. *** **Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and relevant clinical guidelines before making any treatment decisions. Drug information can change, and individual patient factors must be considered.