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# Acetylcysteine
## Overview
Acetylcysteine (NAC) is an mucolytic agent and an antidote for acetaminophen overdose. It is available in oral and intravenous formulations.
## Primary Indications
* **Acetaminophen Overdose:** To prevent or reduce liver toxicity.
* **Mucolytic:** To thin mucus secretions in patients with chronic obstructive pulmonary disease (COPD), cystic fibrosis, and other respiratory conditions.
## Adult Dosing
* **Acetaminophen Overdose:**
* **Oral:** A loading dose of 140 mg/kg is given, followed by 70 mg/kg every 4 hours for a total of 17 doses. The maximum single dose should not exceed 1400 mg.
* **Intravenous:** A loading dose of 150 mg/kg over 1 hour, followed by 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours. Higher doses may be used in severe cases or based on specific protocols.
* **Mucolytic:**
* **Oral/Nebulized:** 200 mg to 400 mg nebulized every 4 to 12 hours.
* **Oral (Effervescent Tablets):** Typically 200 mg three to four times daily.
## Pediatric Dosing
* **Acetaminophen Overdose:** Dosing is the same as adults (140 mg/kg PO loading dose, then 70 mg/kg PO every 4 hours for 17 doses). Intravenous dosing is also typically weight-based and follows adult protocols.
* **Mucolytic:**
* **Nebulized:** 50 mg to 100 mg (3 mL to 6 mL of a 10% solution or 1.5 mL to 3 mL of a 20% solution) nebulized every 3 to 4 hours.
## Dose Adjustments
* **Hepatic Impairment:** No dose adjustment is typically required for acetaminophen overdose, as the primary goal is to saturate the liver with glutathione precursors. For mucolytic use, monitor closely for adverse effects.
* **Renal Impairment:** No specific dose adjustments are routinely recommended, but caution is advised, and monitoring is important.
## Contraindications
* Hypersensitivity to acetylcysteine.
## Adverse Effects
* **Common:** Nausea, vomiting, stomatitis, rhinorrhea, drowsiness.
* **Less Common:** Bronchospasm (especially in patients with asthma), rash, urticaria, anaphylactoid reactions.
* **Intravenous:** Anaphylactoid reactions, flushing, angioedema, hypotension, tachycardia.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb acetylcysteine, reducing its absorption. Separate administration by at least 1 hour.
* **Nitroglycerin:** May potentiate hypotensive effects. Monitor blood pressure closely.
* **Certain Antibiotics:** May decrease the efficacy of some antibiotics (e.g., tetracyclines, aminoglycosides) when administered concurrently. Separate administration by at least 2 hours.
## Monitoring
* **Acetaminophen Overdose:**
* Liver function tests (AST, ALT, bilirubin, INR) should be monitored every 24 hours.
* Acetaminophen levels to guide duration of therapy.
* Monitor for signs of hepatotoxicity.
* **Mucolytic Use:**
* Respiratory status, lung sounds, and sputum production.
* Monitor for bronchospasm.
## Clinical Pearls
* For acetaminophen overdose, early initiation of acetylcysteine (ideally within 8 hours of ingestion) is crucial for optimal efficacy.
* Oral acetylcysteine may have an unpleasant odor and taste; masking with juice or carbonated beverages can improve palatability.
* Intravenous acetylcysteine can cause anaphylactoid reactions; patients should be monitored closely, and premedication with an antihistamine may be considered.
* When nebulizing, consider diluting with sterile water or saline if the odor is poorly tolerated.
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**Disclaimer:** This information is intended for clinical professionals. Always consult the most current prescribing information and local protocols for complete and up-to-date guidance.
