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# Acetylcysteine
## Overview
Acetylcysteine is an antidote for acetaminophen overdose and a mucolytic agent.
## Primary Indications
* Acetaminophen (paracetamol) overdose
* Mucolytic (adjunct therapy in respiratory conditions with excessive or thick mucus)
## Adult Dosing
### Acetaminophen Overdose
* **Intravenous (IV):** Typically administered as a loading dose followed by maintenance doses over 72 hours. A common protocol involves a loading dose of 150 mg/kg IV infused over 1 hour, followed by 50 mg/kg IV infused over 4 hours, and then 100 mg/kg IV infused over 16 hours. The total daily dose should not exceed 600 mg/kg. Specific protocols may vary.
* **Oral (PO):** Loading dose of 140 mg/kg PO, followed by 70 mg/kg PO every 4 hours for 17 doses (total 72 hours).
### Mucolytic
* **Nebulized:** 3 mL of 20% solution or 6 mL of 10% solution every 3-4 hours as needed.
* **Oral (PO):** 200 mg twice daily or three times daily.
* **Intravenous (IV):** Used in specific situations such as contrast-induced nephropathy prophylaxis, but less common for routine mucolytic therapy. Dosing varies by indication and protocol.
## Pediatric Dosing
### Acetaminophen Overdose
* **Intravenous (IV):** Similar to adult dosing on a weight-based calculation (150 mg/kg loading, 50 mg/kg over 4 hours, 100 mg/kg over 16 hours).
* **Oral (PO):** Similar to adult dosing on a weight-based calculation (140 mg/kg loading, 70 mg/kg every 4 hours for 17 doses).
### Mucolytic
* **Nebulized:** 1 mL of 20% solution or 2-3 mL of 10% solution every 3-4 hours as needed.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustment is typically recommended for mild to moderate renal impairment. Caution advised in severe renal impairment.
* **Hepatic Impairment:** No specific dose adjustment is typically recommended. However, patients with hepatic impairment may have altered acetaminophen metabolism and require closer monitoring.
## Contraindications
* Hypersensitivity to acetylcysteine or any component of the formulation.
* Active gastrointestinal bleeding (for oral administration).
## Adverse Effects
* **Common:** Nausea, vomiting, diarrhea, stomatitis, rash, pruritus, urticaria.
* **Serious:** Bronchospasm, anaphylactoid reactions (more common with IV administration, especially with rapid infusion).
* **Nebulized:** Can cause bronchospasm, especially in patients with asthma. Consider concurrent bronchodilator therapy.
## Key Drug Interactions
* **Activated Charcoal:** May bind to oral acetylcysteine, reducing its absorption. Administer acetylcysteine at least 1 hour after activated charcoal.
* **Nitroglycerin:** May potentiate hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels (at baseline and subsequent times based on nomogram).
* Liver function tests (AST, ALT, bilirubin, INR) - typically baseline, 24 hours, and 48-72 hours post-overdose.
* Renal function (BUN, creatinine).
* Glucose.
* Electrolytes.
* **Mucolytic:**
* Respiratory status (breath sounds, sputum production, oxygen saturation).
* Signs of bronchospasm.
## Clinical Pearls
* For acetaminophen overdose, prompt initiation of acetylcysteine is crucial for optimal efficacy, especially if the time of ingestion is unknown or exceeds 24 hours.
* IV acetylcysteine can cause anaphylactoid reactions; monitor patients closely during infusion and have resuscitation equipment readily available. Premedication with antihistamines may be considered.
* Nebulized acetylcysteine can have an unpleasant odor (sulfur-like), which is normal.
* Ensure adequate hydration when using oral acetylcysteine to prevent gastrointestinal upset.
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*Disclaimer: This information is intended for clinical use and does not replace professional medical advice. Always verify current prescribing information and institutional protocols before administering any medication.*
