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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent used to thin mucus and an antidote for acetaminophen overdose.
## Primary Indications
* **Mucolytic:** To liquefy viscous mucus secretions in respiratory conditions (e.g., bronchitis, cystic fibrosis, COPD exacerbations).
* **Acetaminophen Antidote:** To prevent or reduce liver damage following acetaminophen overdose.
## Adult Dosing
* **Mucolytic:**
* **Inhaled:** 3 mL of 20% solution or 6 mL of 10% solution via nebulizer every 4-12 hours as needed. Higher doses may be used in certain situations per institutional protocol.
* **Acetaminophen Antidote:**
* **Oral:** Loading dose of 140 mg/kg, followed by 70 mg/kg every 4 hours for 17 doses (total of 18 doses).
* **Intravenous (IV):** Protocol varies; a common regimen includes a loading dose of 150 mg/kg over 1 hour, followed by 12.5 mg/kg/hour for 4 hours, then 6.25 mg/kg/hour for the subsequent 16 hours. Check specific institutional protocols.
## Pediatric Dosing
* **Mucolytic:**
* **Inhaled:**
* 1 month to 2 years: 1 mL of 20% solution or 2 mL of 10% solution every 2-6 hours.
* 2 years and older: 3 mL of 20% solution or 6 mL of 10% solution every 4-12 hours.
* **Acetaminophen Antidote:**
* **Oral:** Same as adult dosing (140 mg/kg loading dose, then 70 mg/kg every 4 hours for 17 doses).
* **Intravenous (IV):** Refer to specific pediatric IV protocols; dosing is weight-based and requires careful attention to infusion rates.
## Dose Adjustments
No specific dose adjustments are typically required for renal or hepatic impairment for the mucolytic indication. For acetaminophen overdose, dose adjustments are not routinely made based on renal or hepatic function, but careful monitoring is essential.
## Contraindications
* Hypersensitivity to acetylcysteine or its components.
* Active bronchospasm (for inhaled formulations).
## Adverse Effects
* **Inhaled:** Bronchospasm, bronchoconstriction, stomatitis, rhinorrhea, nausea, vomiting, urticaria, rash.
* **Oral/IV (Acetaminophen Antidote):** Anaphylactoid reactions (most common with IV), nausea, vomiting, rash, pruritus, flushing, angioedema, bronchospasm. Rare: Stevens-Johnson syndrome, toxic epidermal necrolysis.
## Key Drug Interactions
* **Activated Charcoal:** If administered within 1 hour of oral acetylcysteine for acetaminophen overdose, it can decrease absorption of acetylcysteine.
* **Nitroglycerin:** May potentiate hypotensive effects.
## Monitoring
* **Mucolytic:** Monitor respiratory status, effectiveness in thinning mucus, and for signs of bronchospasm.
* **Acetaminophen Antidote:** Monitor acetaminophen levels, liver function tests (ALT, AST, bilirubin, INR), and renal function. Monitor for signs of anaphylactoid reactions, especially during IV administration.
## Clinical Pearls
* Dilute inhaled acetylcysteine with sterile water or normal saline if desired by the patient.
* Administer acetylcysteine by nebulizer, direct instillation into tracheostomy tube, or via face mask.
* For IV acetaminophen antidote, pre-medication with an antihistamine may be considered to reduce anaphylactoid reactions.
* The effectiveness of acetylcysteine for acetaminophen overdose is greatest when initiated within 8-10 hours of ingestion, but it should still be administered even if presentation is delayed due to potential ongoing absorption or continued hepatic toxicity.
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_This information is intended for healthcare professionals. It is essential to consult the most current prescribing information and relevant institutional protocols for definitive guidance. Dosing and recommendations may vary._
