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# Acetylcysteine ## Overview Acetylcysteine (NAC) is a mucolytic agent and an antidote for acetaminophen overdose. It acts by breaking disulfide bonds in mucoproteins, decreasing mucus viscosity, and by replenishing glutathione stores depleted by toxic metabolites of acetaminophen. ## Primary Indications * Acetaminophen overdose * Adjunct treatment for mucus plugging in respiratory conditions (e.g., cystic fibrosis, COPD, bronchitis) ## Adult Dosing **Acetaminophen Overdose:** * **Oral:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 72 hours (total of 17 doses). * **Intravenous (IV):** Protocols vary. A common protocol involves a loading dose of 150 mg/kg over 1 hour, followed by 12.5 mg/kg/hour for 4 hours, then 6.25 mg/kg/hour for 16 hours. *Dosing may need to be adjusted based on acetaminophen levels and time since ingestion. Consult local protocol.* **Mucolytic:** * **Inhaled:** 3-10 mL of a 10-20% solution, nebulized every 2-6 hours as needed. * **Oral:** 200 mg to 1200 mg twice daily, depending on indication. ## Pediatric Dosing **Acetaminophen Overdose:** * **Oral:** Same as adult: 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 72 hours (total of 17 doses). * **Intravenous (IV):** Protocols vary. Generally similar to adult dosing, adjusted for weight. *Consult local protocol for specific pediatric IV regimens.* **Mucolytic:** * **Inhaled:** 1-10 mL of a 10-20% solution, nebulized every 2-6 hours as needed. Dose adjusted for age and weight. ## Dose Adjustments No specific dose adjustments are typically required for hepatic or renal impairment, but caution is advised. ## Contraindications * Known hypersensitivity to acetylcysteine. ## Adverse Effects * **Inhaled:** Bronchospasm, bronchoconstriction, stomatitis, rhinorrhea, nausea, vomiting. * **IV:** Anaphylactoid reactions (most common and serious), rash, pruritus, urticaria, angioedema, bronchospasm, dyspnea, hypotension, tachycardia. * **Oral:** Nausea, vomiting, diarrhea, abdominal discomfort. ## Key Drug Interactions * Activated charcoal can reduce the absorption of oral acetylcysteine. * Nitroglycerin may potentiate the vasodilatory effects of acetylcysteine, leading to hypotension and headache. ## Monitoring * **Acetaminophen overdose:** Serum acetaminophen levels, liver function tests (ALT, AST, bilirubin, INR), serum electrolytes, renal function, glucose. * **Mucolytic:** Respiratory status, symptom improvement, potential for bronchospasm. * **IV:** Vital signs (heart rate, blood pressure, respiratory rate), signs of anaphylaxis. ## Clinical Pearls * For IV administration in acetaminophen overdose, prompt initiation is critical, especially if the ingestion time is unknown or levels are concerning. * Dilute IV acetylcysteine for infusion to reduce the risk of anaphylactoid reactions and phlebitis. * Pretreatment with bronchodilators may be necessary in patients with reactive airway disease receiving inhaled acetylcysteine. * A distinct "rotten egg" odor is characteristic and expected. *** Please verify current prescribing information before initiating therapy.