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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucus, decreasing its viscosity. It also acts as an antidote for acetaminophen overdose by replenishing hepatic glutathione stores. ## Primary Indications * **Acetaminophen overdose:** To prevent or reduce liver toxicity. * **Mucolytic:** To thin respiratory secretions in conditions like cystic fibrosis, chronic bronchitis, and pneumonia. ## Adult Dosing **Acetaminophen Overdose:** * **IV Protocol (preferred for initial treatment):** Typically a 3-bag infusion. * **Loading Dose:** 150 mg/kg IV over 1 hour. * **Second Infusion:** 50 mg/kg IV over the next 1 hour (may be given concurrently with loading dose completion). * **Third Infusion:** 100 mg/kg IV over the next 16 hours. * *Note:* Maximum dose can be high and depends on the severity of overdose and patient weight. Specific protocol adherence is critical. * **Oral Protocol (alternative, generally less preferred due to nausea/vomiting):** * **Loading Dose:** 140 mg/kg PO. * **Subsequent Doses:** 70 mg/kg PO every 4 hours for 17 doses (total of 18 doses). * *Note:* Antiemetics are often required. **Mucolytic:** * **Inhalation:** 10% solution: 3-5 mL nebulized every 6-8 hours. 20% solution: 3-5 mL nebulized every 6-8 hours. * **Oral (less common):** 200 mg to 600 mg orally 2-3 times daily. ## Pediatric Dosing **Acetaminophen Overdose (IV Protocol):** * Dosing is the same as adults: 150 mg/kg IV over 1 hour, then 50 mg/kg IV over 1 hour, then 100 mg/kg IV over 16 hours. * *Note:* Consider lower volumes for very small children to avoid fluid overload. Specific protocol adherence is critical. **Mucolytic:** * **Inhalation:** * < 4 years: 1-2 mL of 10% or 20% solution nebulized every 6-8 hours. * > 4 years: 3-5 mL of 10% or 20% solution nebulized every 6-8 hours. * **Oral:** 50 mg/kg to 100 mg/kg orally 2-3 times daily. ## Dose Adjustments * **Renal/Hepatic Impairment:** No specific dose adjustments are typically required, but caution is advised, especially in severe impairment. Monitor for adverse effects. ## Contraindications * Known hypersensitivity to acetylcysteine. * Acute bronchospasm (inhalation). ## Adverse Effects * **IV Acetaminophen Antidote:** Anaphylactoid reactions (rash, urticaria, pruritus, angioedema, bronchospasm, dyspnea, hypotension) are common, particularly during the initial loading dose. Nausea and vomiting are also frequent. * **Inhalation:** Bronchospasm, stomatitis, rhinorrhea, nausea. * **Oral:** Nausea, vomiting, diarrhea, rash. ## Key Drug Interactions * **Activated Charcoal:** May decrease the absorption of oral acetylcysteine. Administer acetylcysteine at least 1 hour after activated charcoal. * **Nitroglycerin:** Potential for additive hypotension. ## Monitoring * **Acetaminophen Overdose:** * Acetaminophen and salicylate levels. * Liver function tests (AST, ALT, bilirubin, INR). * Renal function. * Glucose. * Electrolytes. * Signs and symptoms of anaphylactoid reaction. * **Mucolytic:** * Respiratory status (breath sounds, work of breathing, oxygen saturation). * Effectiveness in thinning secretions. * Signs of bronchospasm. ## Clinical Pearls * For IV administration in acetaminophen overdose, it is crucial to follow a specific institutional protocol. If a patient vomits the initial dose, it may need to be re-administered, often with an antiemetic. * Anaphylactoid reactions to IV acetylcysteine are usually manageable with antihistamines and do not necessitate immediate discontinuation of the antidote, as the risk of hepatotoxicity from untreated acetaminophen overdose is higher. * The smell of acetylcysteine is characteristically unpleasant (sulfurous). * When used as a mucolytic, it is most effective when inhaled. *** **Disclaimer:** This information is intended for healthcare professionals. Always verify current prescribing information and consult with a pharmacist or physician before making any treatment decisions. Dosing and protocols may vary based on institutional guidelines and individual patient factors.