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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent used in respiratory conditions and is the antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen overdose:** To prevent or reduce liver toxicity.
* **Respiratory conditions:** To thin and loosen mucus secretions in conditions such as chronic bronchitis, emphysema, and cystic fibrosis.
## Adult Dosing
### Acetaminophen Overdose
* **Oral:**
* Loading dose: 140 mg/kg
* Subsequent doses: 70 mg/kg every 4 hours for 17 doses (total of 18 doses).
* Maximum single oral dose: 1000 mg.
* **Intravenous (IV):**
* Loading dose: 150 mg/kg over 60 minutes.
* Second infusion: 50 mg/kg over the next 4 hours.
* Third infusion: 100 mg/kg over the next 16 hours.
* Maximum infusion rates for IV administration vary by protocol; consult local guidelines.
### Respiratory Conditions
* **Inhalation:** 1-10 mL of a 10% or 20% solution every 2-6 hours as needed.
* **Nebulization:** Typically 3-5 mL of a 10% or 20% solution.
## Pediatric Dosing
### Acetaminophen Overdose
Dosing is weight-based and identical to adult dosing. Maximum doses are also the same per dose or infusion.
### Respiratory Conditions
* **Inhalation:**
* 0-3 years: 2 mL of a 20% solution or 4 mL of a 10% solution every 2-6 hours.
* 4-12 years: 5 mL of a 20% solution or 10 mL of a 10% solution every 2-6 hours.
* Children > 12 years: Same as adult dosing.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment for acetaminophen overdose. For respiratory indications, dose adjustments are usually based on clinical response and patient tolerance.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active hemorrhage (for IV administration, caution is advised).
## Adverse Effects
* **Inhalation:** Bronchospasm, bronchoconstriction, stomatitis, nausea, vomiting, rhinorrhea.
* **Oral (Acetaminophen Overdose):** Nausea, vomiting, rash, urticaria, pruritus, angioedema.
* **Intravenous (Acetaminophen Overdose):** Anaphylactoid reactions (rash, urticaria, flushing, pruritus, bronchospasm), hypotension, tachycardia, angioedema.
## Key Drug Interactions
* **Activated Charcoal:** May reduce the absorption of orally administered acetylcysteine.
* **Nitroglycerin:** Concomitant use may potentiate the hypotensive effects of nitroglycerin.
## Monitoring
* **Acetaminophen Overdose:**
* Liver function tests (AST, ALT, bilirubin, INR) every 24 hours.
* Serum acetaminophen levels.
* Renal function and electrolytes.
* Monitor for signs of anaphylaxis during IV infusion.
* **Respiratory Conditions:**
* Pulmonary status, breath sounds, and sputum production.
* Assess for bronchospasm.
## Clinical Pearls
* For acetaminophen overdose, oral acetylcysteine is generally preferred if the patient can tolerate it and is not vomiting excessively. IV administration is an alternative, especially in patients with impaired gag reflexes or severe vomiting.
* The antidote treatment for acetaminophen overdose should be initiated as soon as possible, ideally within 8 hours of ingestion.
* Pretreatment with a bronchodilator may be necessary in patients with reactive airway disease receiving inhaled acetylcysteine.
* Dilute nebulized acetylcysteine with sterile water for injection or normal saline if needed for administration.
* The smell of acetylcysteine is strong and unpleasant; this can affect patient compliance.
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*Disclaimer: This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and local institutional protocols before administering any medication.*
