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# Acetylcysteine ## Overview Acetylcysteine (NAC) is a mucolytic agent and an antidote for acetaminophen overdose. It also has investigational uses in various conditions due to its antioxidant properties. ## Primary Indications * **Acetaminophen overdose:** To prevent or reduce liver toxicity. * **Mucolytic:** To thin and loosen mucus in respiratory conditions such as chronic bronchitis, emphysema, and cystic fibrosis. ## Adult Dosing **Acetaminophen Overdose:** * **Intravenous (IV):** Typically a 3-bag, 72-hour protocol. * **Loading Dose:** 150 mg/kg IV over 1 hour. * **Second Infusion:** 50 mg/kg IV over the next 1 hour. * **Third Infusion:** 100 mg/kg IV over the next 16 hours. * *Note:* Max dose not explicitly defined by protocol, but total volume and concentration should be considered for fluid management. Local protocols may vary. * **Oral (PO):** Also a 72-hour protocol, typically involves higher initial doses. * **Loading Dose:** 140 mg/kg PO. * **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses. * *Note:* Maximum single oral dose is typically 140 mg/kg, not to exceed 12 grams per day. This route is less common due to potential for vomiting and absorption issues. **Mucolytic:** * **Inhaled:** 10% solution: 3-5 mL inhaled via nebulizer every 3-4 hours. 20% solution: 3-5 mL inhaled via nebulizer every 3-4 hours. * **Oral:** 200 mg (equivalent to 1 capsule or effervescent tablet) 2-3 times daily. ## Pediatric Dosing **Acetaminophen Overdose:** Dosing is the same as adult dosing (150 mg/kg loading, 50 mg/kg second infusion, 100 mg/kg third infusion IV). However, concentrations may need adjustment to manage fluid volume in neonates and small infants. **Mucolytic:** * **Inhaled:** * Children < 1 year: 1-2 mL of 10% solution via nebulizer every 2-6 hours. * Children 1-2 years: 2-4 mL of 10% solution via nebulizer every 2-6 hours. * Children > 2 years: Dosing similar to adults (3-5 mL of 10% or 20% solution). * **Oral:** Generally not recommended for children < 2 years. For children > 2 years, similar to adult dosing (e.g., 200 mg BID-TID). ## Dose Adjustments * **Renal Impairment:** No specific dose adjustment is typically recommended for mild to moderate renal impairment. Use with caution in severe renal impairment. * **Hepatic Impairment:** No specific dose adjustment is typically recommended. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. ## Adverse Effects * **Common:** Nausea, vomiting, diarrhea, stomatitis, rash, pruritus, fever, rhinorrhea. * **Less Common/Serious:** Bronchospasm (especially in asthmatics), anaphylactoid reactions (particularly with IV administration, often manifesting as rash, urticaria, angioedema, bronchospasm, tachycardia, hypotension). * **IV Administration:** Can cause flushing, headache, and rarely, seizures. ## Key Drug Interactions * **Activated Charcoal:** May reduce the absorption of oral acetylcysteine. If both are used, administer acetylcysteine after charcoal has been removed from the GI tract. * **Nitroglycerin:** May potentiate the vasodilatory effects and decrease plasma levels of nitroglycerin, potentially reducing its efficacy. Monitor for hypotension and consider nitroglycerin dose reduction. * **Antitussives:** May suppress cough reflex, potentially leading to retained secretions when used as a mucolytic. ## Monitoring * **Acetaminophen Overdose:** * **Liver Function Tests (LFTs):** AST, ALT, bilirubin, INR, prothrombin time (PT) regularly during and after treatment. * **Acetaminophen levels:** To confirm overdose and assess effectiveness of antidote. * **Renal function:** BUN, creatinine. * **Electrolytes:** Sodium, potassium. * **Clinical signs of liver damage:** Jaundice, encephalopathy. * **Mucolytic Use:** * **Pulmonary status:** Auscultation, respiratory rate, oxygen saturation, sputum production. * **Bronchospasm:** Monitor for signs of wheezing or dyspnea. ## Clinical Pearls * For IV administration in acetaminophen overdose, dilute the final concentration to avoid fluid overload, especially in children. A common dilution is 150 mg/kg in 200 mL or 300 mL of D5W or NS. * Administer IV acetylcysteine slowly initially to mitigate anaphylactoid reactions. Have resuscitation equipment readily available. * Oral acetylcysteine may be flavored or mixed with juice to improve palatability and reduce nausea. * Consider co-administration with bronchodilators if the patient has reactive airway disease and is receiving inhaled acetylcysteine. *** *Disclaimer: This information is intended for clinical reference and does not replace professional medical judgment. Always consult the most current prescribing information and institutional protocols before administering any medication.*