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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucus, reducing its viscosity. It is also an antidote for acetaminophen overdose.
## Primary Indications
* **Mucolytic:** Management of conditions involving thick, viscous mucus (e.g., chronic bronchitis, emphysema, cystic fibrosis, tracheostomy care).
* **Acetaminophen Overdose Antidote:** Prevention of liver damage following acetaminophen overdose.
## Adult Dosing
* **Mucolytic:**
* Inhalation: 3 mL of 20% solution or 6 mL of 10% solution nebulized every 3-4 hours as needed. Alternatively, administer via continuous nebulization at a dose of 1 mL of 20% solution per hour.
* Direct Instillation: 1-2 mL of 20% solution instilled into the trachea every 1-4 hours.
* **Acetaminophen Overdose Antidote:** Administered intravenously or orally.
* **IV (preferred for initial management due to better efficacy and tolerability):**
* Loading Dose: 150 mg/kg over 1 hour.
* Second Infusion: 50 mg/kg over the next 4 hours.
* Third Infusion: 100 mg/kg over the subsequent 16 hours.
* Maximum dose: Not to exceed 1200 mg per infusion for adults.
* **Oral:**
* Loading Dose: 140 mg/kg.
* Subsequent Doses: 70 mg/kg every 4 hours for 17 doses.
* Maximum dose: 200 mg/kg per dose for children, no explicit maximum stated for adults in this regimen, but total daily intake should be considered.
## Pediatric Dosing
* **Mucolytic:**
* Inhalation: 1 mL of 20% solution or 2-3 mL of 10% solution nebulized every 3-4 hours. For continuous nebulization, 1 mL of 20% solution per hour.
* **Acetaminophen Overdose Antidote:**
* **IV:** Dosing is the same as adults (150 mg/kg, then 50 mg/kg, then 100 mg/kg) with a maximum dose of 150 mg/kg per infusion.
* **Oral:** Same as adults (140 mg/kg loading, then 70 mg/kg every 4 hours for 17 doses).
* Maximum dose: 200 mg/kg per dose.
## Dose Adjustments
* No dose adjustment is typically required for renal or hepatic impairment for the mucolytic indication.
* For acetaminophen overdose, dose adjustments are based on patient weight and the duration of overdose exposure.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active gastrointestinal bleeding (oral administration).
## Adverse Effects
* **Inhaled:** Bronchospasm, rhinorrhea, nausea, vomiting, stomatitis.
* **IV (for acetaminophen overdose):** Anaphylactoid reactions (rash, urticaria, pruritus, angioedema, bronchospasm, dyspnea, hypotension), flushing, fever. Rarely, seizures, hepatic necrosis.
* **Oral (for acetaminophen overdose):** Nausea, vomiting, diarrhea.
## Key Drug Interactions
* **Activated Charcoal:** Can adsorb oral acetylcysteine, reducing its absorption. Separate administration by at least 1 hour.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension.
## Monitoring
* **Mucolytic:** Respiratory status, sputum viscosity and ease of expectoration, presence of bronchospasm.
* **Acetaminophen Overdose:**
* Serum acetaminophen levels.
* Liver function tests (AST, ALT, bilirubin, INR) at baseline and periodically.
* Renal function and electrolytes.
* Vital signs, particularly during IV infusion for anaphylactoid reactions.
## Clinical Pearls
* The smell of acetylcysteine is characteristically sulfurous and may be unpleasant.
* For inhaled use, patients with asthma or reactive airway disease may require concomitant bronchodilator therapy.
* Oral acetylcysteine for acetaminophen overdose has a strong, unpleasant taste and odor and frequently causes nausea and vomiting; antiemetics may be beneficial.
* IV acetylcysteine for acetaminophen overdose requires careful monitoring for anaphylactoid reactions. Pretreatment with antihistamines and corticosteroids may be considered in some patients.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult current prescribing information and your institution's protocols for definitive guidance.
