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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, reducing mucus viscosity. As an antidote, it replenishes hepatic glutathione stores depleted by acetaminophen metabolism. ## Primary Indications * **Acetaminophen Overdose:** To prevent or reduce liver toxicity. * **Mucolytic:** To thin respiratory secretions in conditions such as chronic bronchitis, emphysema, pneumonia, and cystic fibrosis. ## Adult Dosing ### Acetaminophen Overdose * **Loading Dose:** 150 mg/kg intravenously (IV) infused over 1 hour. * **Second Dose:** 50 mg/kg IV infused over 16 hours. * **Third Dose:** 100 mg/kg IV infused over the next 16 hours (if needed, depending on acetaminophen levels and liver function). * **Alternative Oral Protocol:** 140 mg/kg loading dose orally, followed by 70 mg/kg orally every 4 hours for 17 doses. *Oral administration is less preferred due to potential for vomiting and poor absorption.* * **Maximum Dose:** Typically no strict maximum daily dose, but follow specific protocol guidelines. ### Mucolytic * **Inhaled:** 1 to 10 mL of a 10% or 20% solution nebulized every 2 to 6 hours. * **Intratracheal:** 1 to 2 mL of a 10% or 20% solution every 1 to 4 hours. ## Pediatric Dosing ### Acetaminophen Overdose * Dosing is the same as adult dosing, calculated by weight (150 mg/kg IV loading dose, then 50 mg/kg IV over 16 hours, then 100 mg/kg IV over 16 hours). * Oral dosing is also the same as adult: 140 mg/kg orally loading dose, then 70 mg/kg orally every 4 hours for 17 doses. ### Mucolytic * **Inhaled:** * **< 1 year:** 1 mL of a 10% solution nebulized every 2 to 6 hours. * **1-12 years:** 1 to 2 mL of a 10% solution nebulized every 2 to 6 hours. * **> 12 years:** 1 to 10 mL of a 10% or 20% solution nebulized every 2 to 6 hours. ## Dose Adjustments * **Renal Impairment:** No specific dose adjustments are typically required for renal impairment, but caution may be warranted due to potential accumulation. * **Hepatic Impairment:** No specific dose adjustments are typically required for hepatic impairment in the context of acetaminophen overdose, as the goal is to support the liver. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. * **Oral Formulations:** Patients with active peptic ulcer disease or gastrointestinal bleeding. ## Adverse Effects * **IV:** Anaphylactoid reactions (rash, urticaria, pruritus, bronchospasm, angioedema, dyspnea, hypotension) are common, particularly with rapid infusion. Nausea, vomiting. * **Inhaled:** Bronchospasm, stomatitis, nausea, vomiting, rhinorrhea. * **Oral:** Nausea, vomiting, diarrhea. ## Key Drug Interactions * **Activated Charcoal:** May adsorb acetylcysteine, reducing oral absorption. If both are indicated, administer activated charcoal at least 1 hour after oral acetylcysteine. * **Nitroglycerin:** Concomitant use may potentiate hypotensive effects. ## Monitoring * **Acetaminophen Overdose:** Serum acetaminophen levels, liver function tests (AST, ALT, bilirubin, INR), prothrombin time, glucose, electrolytes, renal function. Clinical signs of anaphylaxis. * **Mucolytic:** Respiratory status, oxygen saturation, presence of bronchospasm. ## Clinical Pearls * For IV administration in acetaminophen overdose, it is critical to initiate treatment as soon as possible, ideally within 8 hours of ingestion, for optimal efficacy. * The IV formulation can cause anaphylactoid reactions. Slow the infusion rate and administer antihistamines if symptoms occur. Do not discontinue treatment unless severe. * When nebulizing acetylcysteine, patients with asthma or reactive airway disease may experience bronchospasm. Administering a bronchodilator before or concurrently may be necessary. * The smell of acetylcysteine is characteristically unpleasant (sulfurous) and can contribute to nausea and vomiting, especially with oral administration. *** *Disclaimer: This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and institutional protocols for definitive guidance.*