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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucus, decreasing its viscosity. It is also an antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver damage.
* **Mucolytic:** To thin respiratory secretions in patients with conditions such as chronic bronchitis, emphysema, cystic fibrosis, and pneumonia.
## Adult Dosing
### Acetaminophen Overdose
* **Initial Loading Dose:** 150 mg/kg IV infused over 1 hour.
* **Second Dose:** 50 mg/kg IV infused over 16 hours.
* **Third Dose:** 100 mg/kg IV infused over 16 hours (continue for a total of 72 hours if needed).
* **Oral Protocol:** Alternatively, a 72-hour oral protocol exists, with initial doses of 140 mg/kg followed by 70 mg/kg every 4 hours for 17 doses.
### Mucolytic
* **Inhalation:** 1-10 mL of a 20% solution or 2-20 mL of a 10% solution nebulized every 2-6 hours. Maximum of 30 mL per day.
## Pediatric Dosing
### Acetaminophen Overdose
* Dosing is based on weight, same as adult dosing (150 mg/kg IV, then 50 mg/kg IV, then 100 mg/kg IV over 72 hours).
* Oral protocol also mirrors adult dosing.
### Mucolytic
* **Inhalation:** 1-10 mL of a 20% solution or 2-20 mL of a 10% solution nebulized every 2-6 hours.
## Dose Adjustments
* No dose adjustment is typically needed for renal or hepatic impairment for the mucolytic indication. For acetaminophen overdose, continued monitoring and potential dose adjustments are based on acetaminophen and metabolite levels, and clinical status.
## Contraindications
* Known hypersensitivity to acetylcysteine.
## Adverse Effects
* **Inhalation:** Bronchospasm, nausea, vomiting, stomatitis, rhinorrhea.
* **IV (Acetaminophen Overdose):** Anaphylactoid reactions (rash, pruritus, urticaria, angioedema, bronchospasm, dyspnea), nausea, vomiting, flushing, tachycardia, hypotension. Serious anaphylactoid reactions can occur.
## Key Drug Interactions
* **Activated Charcoal:** May bind to oral acetylcysteine and reduce its absorption.
## Monitoring
* **Acetaminophen Overdose:** Serial acetaminophen levels, liver function tests (ALT, AST, bilirubin, INR), glucose, electrolytes, and renal function. Monitor for signs of anaphylactoid reaction.
* **Mucolytic:** Patient's response to therapy (ease of expectoration, change in mucus consistency), and for signs of bronchospasm.
## Clinical Pearls
* Dilute IV acetylcysteine according to protocol to reduce risk of phlebitis and anaphylactoid reactions.
* Consider premedication with an H1 antihistamine for patients receiving IV acetylcysteine for acetaminophen overdose to mitigate anaphylactoid reactions.
* The smell of acetylcysteine is characteristically unpleasant (rotten eggs).
* For inhalation, if bronchospasm occurs, administration of a bronchodilator may be necessary.
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*Please verify current prescribing information for the most up-to-date dosing and safety guidelines.*
