Acetyl%2525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252525252520cysteine

# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucoproteins, decreasing mucus viscosity. It also acts as an antidote for acetaminophen overdose by replenishing glutathione stores. ## Primary Indications * **Acetaminophen Overdose:** As an antidote to prevent or mitigate liver toxicity. * **Mucolytic:** To thin mucus in conditions like cystic fibrosis, chronic obstructive pulmonary disease (COPD), and pneumonia. ## Adult Dosing * **Acetaminophen Overdose:** * **Loading Dose:** 150 mg/kg intravenously (IV) over 1 hour. * **Second Dose:** 50 mg/kg IV over the next 1 hour. * **Third Dose:** 100 mg/kg IV over the next 16 hours (total infusion time 17 hours). * *Note:* Dosing may vary based on acetaminophen levels and time since ingestion. Some protocols may extend the infusion or use oral acetylcysteine. * **Mucolytic:** * **Nebulized:** 3-10 mL of a 20% solution or 6-12 mL of a 10% solution every 2-6 hours. * **Oral:** 200 mg to 1000 mg (orally disintegrating tablet or effervescent tablet) 2-4 times daily. The 600 mg once-daily formulation is also common. ## Pediatric Dosing * **Acetaminophen Overdose:** Dosing is identical to adults on a mg/kg basis. * **Loading Dose:** 150 mg/kg IV over 1 hour. * **Second Dose:** 50 mg/kg IV over the next 1 hour. * **Third Dose:** 100 mg/kg IV over the next 16 hours. * *Note:* For children weighing less than 40 kg, the maximum dose for each IV infusion should not exceed the adult maximum for that infusion (e.g., maximum loading dose is 150 mg/kg, but not to exceed 150 mg/kg of a 150 lb adult; subsequent doses are calculated similarly). For nebulized use, typical doses range from 1 mL of 20% solution (200 mg) to 5 mL of 20% solution (1000 mg) via nebulizer every 2-6 hours. * **Mucolytic:** * **Nebulized:** (See adult dosing, adjusted for weight). Typical doses: Neonates and infants < 1 month: 1 mL of 10% or 20% solution every 2-6 hours. Older children: 3-10 mL of 20% solution or 6-12 mL of 10% solution every 2-6 hours. * **Oral:** Dosing varies by age and formulation. Commonly: 50 mg/kg per dose orally every 4-12 hours. Max 800 mg/day. ## Dose Adjustments * No specific dose adjustments are typically required for hepatic or renal impairment for the antidote indication, as the goal is to overcome a critical overdose. * For mucolytic use, adjustments may be based on patient tolerance and response. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. * Active gastrointestinal bleeding (for oral formulations). ## Adverse Effects * **IV Administration:** Anaphylactoid reactions (rash, pruritus, angioedema, bronchospasm, wheezing), flushing, hypotension, tachycardia. These are often infusion-rate related. Nausea and vomiting can occur. * **Nebulized Administration:** Bronchospasm, particularly in patients with reactive airway disease. Nausea and vomiting. Unpleasant odor. * **Oral Administration:** Nausea, vomiting, diarrhea, stomatitis, rash. ## Key Drug Interactions * **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its efficacy. Administer oral acetylcysteine at least 1 hour after activated charcoal. * **Nitroglycerin:** Potentiation of vasodilatory effects may occur, leading to hypotension and headache. ## Monitoring * **Acetaminophen Overdose:** * Serum acetaminophen levels (at appropriate time points). * Liver function tests (AST, ALT, bilirubin, INR). * Renal function and electrolytes. * Blood glucose (especially with IV administration). * Signs of anaphylactoid reaction during IV infusion. * **Mucolytic Use:** * Pulmonary status and mucus expectoration. * Signs of bronchospasm. ## Clinical Pearls * IV acetylcysteine for acetaminophen overdose is most effective when initiated within 8 hours of ingestion. However, it should still be administered even if later, as it can still provide benefit. * Pretreatment with an H1 and/or H2 blocker and/or a corticosteroid may reduce the incidence and severity of anaphylactoid reactions with IV acetylcysteine. * The characteristic sulfurous odor of acetylcysteine is normal and may be reduced by covering the nebulizer cup or using flavored preparations. * For inhaled acetylcysteine, bronchospasm can be treated with a bronchodilator. *** *Please verify current prescribing information with the product monograph or official guidelines before administration.*