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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent and an antidote for acetaminophen overdose. It is available in oral and intravenous formulations. ## Primary Indications * **Acetaminophen Overdose:** The primary indication for intravenous acetylcysteine. * **Mucolytic:** Used to thin and loosen mucus in respiratory conditions such as chronic bronchitis, emphysema, and cystic fibrosis. Often administered via nebulizer. ## Adult Dosing ### Acetaminophen Overdose (Intravenous) * **Loading Dose:** 150 mg/kg IV over 1 hour. * **Second Infusion:** 50 mg/kg IV over the next 4 hours. * **Third Infusion:** 100 mg/kg IV over the next 16 hours. * **Maximum:** Total daily dose can be up to 300 mg/kg. ### Mucolytic (Nebulized) * **Dose:** 10% solution: 3-5 mL every 4-12 hours. 20% solution: 2-3 mL every 4-12 hours. * **Alternate:** Can be administered undiluted or diluted with sterile water or normal saline. ## Pediatric Dosing ### Acetaminophen Overdose (Intravenous) Dosing is the same as adults (150 mg/kg, 50 mg/kg, 100 mg/kg over specified intervals). ### Mucolytic (Nebulized) * **Dose:** * **10% solution:** 1-2 mL every 2-6 hours. * **20% solution:** 1 mL every 2-6 hours. ## Dose Adjustments No dose adjustments are typically required for renal or hepatic impairment, but caution is advised. ## Contraindications * Known hypersensitivity to acetylcysteine. * Active gastrointestinal bleeding (for oral formulation, though evidence is mixed). ## Adverse Effects * **Intravenous:** Anaphylactoid reactions (rash, urticaria, pruritus, angioedema, bronchospasm, dyspnea, wheezing), hypotension, tachycardia. Nausea and vomiting are common. * **Nebulized:** Bronchospasm, nausea, vomiting, stomatitis. ## Key Drug Interactions * **Activated Charcoal:** May bind acetylcysteine if given concurrently for overdose, potentially reducing its absorption. Separate administration by at least 2 hours. * **Nitroglycerin:** May potentiate hypotensive effects. ## Monitoring * **Acetaminophen Overdose:** Acetaminophen and its toxic metabolite (NAPQI) levels, liver function tests (LFTs), prothrombin time (PT), international normalized ratio (INR), glucose, electrolytes, renal function. * **Mucolytic:** Respiratory status, presence of bronchospasm. ## Clinical Pearls * For IV acetaminophen overdose, initiation within 8 hours of ingestion provides the best outcome. * Protocols for IV acetylcysteine may vary by institution. Always consult local guidelines. * Anaphylactoid reactions are common with IV administration and are typically managed with dose reduction, slowing the infusion, or antihistamines. Discontinuation is rarely necessary. * Nebulized acetylcysteine has an unpleasant odor due to sulfur. *** *Please verify current prescribing information for the most up-to-date details.*