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# Acetylcysteine ## Overview Acetylcysteine is a mucolytic agent used to break down thick mucus in the airways. It is also an antidote for acetaminophen overdose. ## Primary Indications * **Mucolytic:** Adjunct therapy for respiratory conditions associated with tenacious mucus secretions (e.g., chronic bronchitis, cystic fibrosis, pneumonia, tracheostomy care). * **Acetaminophen Overdose Antidote:** To prevent or reduce liver damage following acetaminophen overdose. ## Adult Dosing * **Mucolytic (Inhaled):** 3 to 5 mL of a 20% solution or 6 to 10 mL of a 10% solution nebulized every 4 to 12 hours. Dosing frequency and concentration may vary based on patient response and tolerance. * **Acetaminophen Overdose:** * **Oral:** Loading dose of 140 mg/kg, followed by 70 mg/kg every 4 hours for 17 doses (total 71 hours). * **Intravenous (IV):** Protocols vary, but commonly involve a loading dose of 150 mg/kg infused over 1 hour, followed by 12.5 mg/kg/hour for 4 hours, then 6.25 mg/kg/hour for 16 hours. **(IV dosing is often protocol-dependent and may vary by institution.)** ## Pediatric Dosing * **Mucolytic (Inhaled):** 10% solution: 1 to 2 mL nebulized every 2 to 6 hours. 20% solution: 1 mL nebulized every 2 to 6 hours. Dosing should be individualized. * **Acetaminophen Overdose:** * **Oral:** Same as adult dosing (140 mg/kg loading dose, then 70 mg/kg every 4 hours for 17 doses). * **Intravenous (IV):** Same as adult IV dosing (150 mg/kg over 1 hour, then 12.5 mg/kg/hour for 4 hours, then 6.25 mg/kg/hour for 16 hours). **(IV dosing is often protocol-dependent and may vary by institution.)** ## Dose Adjustments No specific dose adjustments are typically required for hepatic or renal impairment for mucolytic use. For acetaminophen overdose, dose adjustments are generally not indicated for impaired renal or hepatic function, but careful monitoring is crucial. ## Contraindications * Hypersensitivity to acetylcysteine or any component of the formulation. * Active gastrointestinal bleeding (for oral administration). ## Adverse Effects * **Inhaled:** Bronchospasm (especially in asthmatics), stomatitis, nausea, vomiting, rhinorrhea. * **Oral (Acetaminophen Antidote):** Nausea, vomiting, diarrhea. Anaphylactoid reactions can occur, including rash, urticaria, pruritus, angioedema, bronchospasm, and dyspnea. * **Intravenous (Acetaminophen Antidote):** Anaphylactoid reactions (most common), flushing, pruritus, urticaria, rash, hypotension, tachycardia, bronchospasm, angioedema. Rare instances of anaphylaxis and death have been reported. ## Key Drug Interactions * **Activated Charcoal:** May reduce the absorption of orally administered acetylcysteine. * **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension and headache. ## Monitoring * **Mucolytic Use:** Respiratory status, sputum characteristics, signs of bronchospasm. * **Acetaminophen Overdose:** * Serum acetaminophen levels (timed according to ingestion). * Liver function tests (AST, ALT, bilirubin, INR) at baseline and typically every 24 hours for at least 72 hours. * Renal function. * Signs of anaphylactoid reaction (especially with IV administration). ## Clinical Pearls * For inhaled acetylcysteine, bronchodilators should be administered first to prevent bronchospasm. * The effectiveness of oral acetylcysteine for acetaminophen overdose is greatest when initiated within 8-10 hours of ingestion. * IV acetylcysteine for acetaminophen overdose has shown comparable efficacy to oral administration and may be preferred in patients who cannot tolerate oral agents. * Pretreatment with antihistamines or corticosteroids may be considered for patients with a history of hypersensitivity reactions to IV acetylcysteine. *** **Disclaimer:** This information is for educational purposes only and does not substitute for professional medical advice. Always consult with a qualified healthcare provider and verify the current prescribing information and institutional protocols before making any treatment decisions.