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# Acetylcysteine ## Overview Acetylcysteine (NAC) is a mucolytic agent and an antidote for acetaminophen overdose. It is thought to replenish glutathione stores and directly bind to toxic metabolites of acetaminophen. ## Primary Indications * Acetaminophen overdose * Adjunct in the management of severe mucoviscidosis (mucolytic) ## Adult Dosing * **Acetaminophen Overdose:** Typically a 3-bag protocol. * **Loading Dose:** 150 mg/kg IV infused over 1 hour. * **Second Infusion:** 50 mg/kg IV infused over the next 4 hours. * **Third Infusion:** 100 mg/kg IV infused over the next 16 hours. * **Maximum Dose:** Total daily dose should not exceed 150 mg/kg for the first 24 hours, but higher doses may be used in severe overdoses or if acetaminophen levels remain elevated. Specific total maximums are not well-defined and may vary by protocol. * **Mucolytic (Nebulized):** 10% solution, 3-5 mL every 4-6 hours, or 20% solution, 2-4 mL every 4-6 hours. ## Pediatric Dosing * **Acetaminophen Overdose:** Dosing is the same as adults (150 mg/kg, 50 mg/kg, 100 mg/kg over respective time periods). However, the loading dose should not exceed 150 mg/kg. Maximum concentrations for IV administration are important to avoid fluid overload. * **Mucolytic (Nebulized):** 10% solution, 1-2 mL every 2-6 hours. ## Dose Adjustments No specific dose adjustments are typically required for hepatic or renal impairment, but caution may be advised in patients with severe underlying liver disease given the high doses used in overdose treatment. ## Contraindications Hypersensitivity to acetylcysteine. ## Adverse Effects * **IV Administration:** Anaphylactoid reactions (rash, pruritus, bronchospasm, angioedema, hypotension) are common, especially during the loading dose. Nausea and vomiting can also occur. * **Nebulized:** Bronchospasm (particularly in asthmatics), stomatitis, nausea, vomiting. ## Key Drug Interactions * **Activated Charcoal:** May bind to acetylcysteine and reduce its absorption/efficacy if administered concurrently. Separate administration by at least 2 hours. ## Monitoring * **Acetaminophen Overdose:** * Acetaminophen levels (obtain at 4 hours post-ingestion, and then periodically as clinically indicated). * Liver function tests (LFTs) and coagulation studies (PT/INR, PTT) for severe overdoses or prolonged treatment. * Renal function. * Vital signs, especially during IV infusion for anaphylactoid reactions. * **Mucolytic:** Respiratory status, oxygen saturation. ## Clinical Pearls * For acetaminophen overdose, IV acetylcysteine is generally preferred over oral due to better palatability and lower incidence of nausea/vomiting. * The antidote protocol for acetaminophen overdose is time-sensitive; initiate treatment promptly based on ingestion time and serum acetaminophen levels. * Always consider the possibility of anaphylactoid reactions with IV acetylcysteine and be prepared to manage them. Premedication with an antihistamine and/or corticosteroid is sometimes used but controversial. * For nebulized acetylcysteine, consider concurrent administration of a bronchodilator to mitigate bronchospasm. * The duration of IV acetylcysteine treatment for acetaminophen overdose is typically 72 hours but can be extended if acetaminophen levels are still detectable or if LFTs are deranged. *** *This information is for educational purposes and does not substitute for current prescribing information. Always consult the official drug monograph and institutional protocols before administering any medication.*