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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucus, reducing its viscosity. It is also the antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver toxicity.
* **Adjunct in Bronchopulmonary Disease:** To reduce the viscosity of mucus in conditions like cystic fibrosis, chronic bronchitis, and emphysema.
## Adult Dosing
**Acetaminophen Overdose:**
* **Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Dose:** 50 mg/kg IV infused over 16 hours.
* **Third Dose:** 50 mg/kg IV infused over 16 hours.
* *Note:* The duration of therapy may be extended if acetaminophen levels remain toxic or if liver injury progresses. Protocols may vary; consult local guidelines.
**Adjunct in Bronchopulmonary Disease:**
* **Inhalation:** 1 to 10 mL of a 20% solution or 2 to 20 mL of a 10% solution, nebulized every 3 to 4 hours, up to 6 times daily.
## Pediatric Dosing
**Acetaminophen Overdose:**
* Dosing is the same as for adults (150 mg/kg IV over 1 hour, followed by 50 mg/kg IV over 16 hours, repeated once).
* *Note:* Maximum doses for loading and maintenance should be considered based on weight. Consult local guidelines.
**Adjunct in Bronchopulmonary Disease:**
* **Inhalation:**
* 10% solution: 1 to 2 mL nebulized every 2 to 6 hours.
* 20% solution: 1 mL nebulized every 2 to 6 hours.
* *Note:* Concentration and frequency may vary based on patient tolerance and response.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment in the setting of acetaminophen overdose, as the benefit of the antidote outweighs potential risks. For mucolytic use, adjustments are based on clinical response and tolerance.
## Contraindications
* Known hypersensitivity to acetylcysteine.
* Use with caution in patients with asthma or a history of bronchospasm, especially with inhaled formulations.
## Adverse Effects
**IV Administration:**
* Anaphylactoid reactions (rash, urticaria, bronchospasm, angioedema), hypotension, tachycardia, dyspnea.
* Flushing, nausea, vomiting.
* Rarely, seizures, facial edema, gastrointestinal hemorrhage.
**Inhalation:**
* Bronchospasm, particularly in patients with asthma.
* Nausea, vomiting, stomatitis, rhinorrhea.
* Chest tightness, coughing.
## Key Drug Interactions
* **Activated Charcoal:** May reduce the absorption of oral acetylcysteine if given concurrently in acetaminophen overdose. Administer charcoal and acetylcysteine separately.
* **Nitroglycerin:** May potentiate the hypotensive effects of nitroglycerin.
## Monitoring
* **Acetaminophen Overdose:** Serial acetaminophen and ALT/AST levels, prothrombin time, bilirubin, creatinine, glucose, and clinical signs of liver injury. Monitor for adverse reactions to IV acetylcysteine.
* **Bronchopulmonary Disease:** Clinical assessment of mucus viscosity and airway clearance, pulmonary function tests, and monitoring for adverse respiratory effects.
## Clinical Pearls
* For IV administration in acetaminophen overdose, a 20-hour protocol is common, but duration may extend. Always consult local protocols.
* Pre-treatment with an H1 antagonist may reduce the incidence of anaphylactoid reactions with IV acetylcysteine. Bronchodilators should be available for patients receiving inhaled acetylcysteine.
* The smell of acetylcysteine is characteristically unpleasant (sulfurous), which may lead to poor adherence with nebulized therapy.
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**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and institutional protocols before administering any medication.
