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# Acetylcysteine
## Overview
Acetylcysteine (N-acetylcysteine, NAC) is a mucolytic agent that also acts as an antidote for acetaminophen overdose. It is thought to replenish glutathione stores, which are depleted during acetaminophen toxicity.
## Primary Indications
* **Acetaminophen overdose:** As an antidote.
* **Mucolytic:** To thin and loosen mucus in the airways (e.g., in COPD, cystic fibrosis, pneumonia).
## Adult Dosing
### Acetaminophen Overdose
**Intravenous (IV) administration is preferred for overdose.** The standard protocol involves an initial loading dose followed by subsequent infusions. A common regimen is:
* **Loading dose:** 150 mg/kg IV over 1 hour.
* **Second infusion:** 50 mg/kg IV over 4 hours.
* **Third infusion:** 100 mg/kg IV over 16 hours.
* **Maximum dose:** Total daily dose should not exceed 300 mg/kg.
* **Note:** Specific protocols and concentrations may vary; confirm local guidelines. Some protocols use a 72-hour regimen.
### Mucolytic
* **Inhaled:** 3 mL to 5 mL of a 20% solution or 6 mL of a 10% solution, nebulized every 4 to 6 hours. Higher doses may be used in some cystic fibrosis protocols.
* **Oral:** 200 mg to 400 mg twice daily or three times daily.
## Pediatric Dosing
### Acetaminophen Overdose
Dosing is the same as adult dosing, calculated by weight (150 mg/kg loading dose, then 50 mg/kg, then 100 mg/kg). The total duration of infusion is typically 72 hours.
### Mucolytic
* **Inhaled:** 1 mL to 2 mL of a 20% solution or 3 mL of a 10% solution, nebulized every 4 to 6 hours.
## Dose Adjustments
* **Renal or Hepatic Impairment:** No specific dose adjustment is typically required for acetaminophen overdose. For mucolytic use, caution may be advised, but no specific adjustments are standard.
## Contraindications
* Hypersensitivity to acetylcysteine or its components.
## Adverse Effects
* **IV administration (especially for overdose):** Anaphylactoid reactions (rash, urticaria, pruritus, bronchospasm, angioedema, dyspnea, wheezing) are common and can be severe. Nausea and vomiting are also frequent. Hypotension and tachycardia can occur.
* **Inhaled administration:** Bronchospasm (especially in patients with asthma), stomatitis, nausea, vomiting, rhinorrhea.
* **Oral administration:** Nausea, vomiting, diarrhea, abdominal pain, rash.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb acetylcysteine, reducing its efficacy. Separate administration by at least 1 hour.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension.
## Monitoring
* **Acetaminophen Overdose:**
* Serum acetaminophen levels (obtain baseline and serial levels).
* Liver function tests (LFTs) (ALT, AST, bilirubin, INR).
* Renal function (BUN, creatinine).
* Glucose.
* Electrolytes.
* Monitor for signs of anaphylactoid reactions during IV infusion.
* **Mucolytic:**
* Pulmonary function.
* Patient's subjective response (ease of expectoration).
* Monitor for bronchospasm.
## Clinical Pearls
* For IV acetaminophen overdose, the loading dose is crucial and should be administered rapidly over 1 hour.
* Anaphylactoid reactions to IV acetylcysteine are common but usually manageable with slower infusion rates and antihistamines/bronchodilators. Discontinuation of the infusion may be necessary for severe reactions.
* Always reconstitute and dilute IV acetylcysteine according to manufacturer guidelines and local protocols.
* The oral formulation for acetaminophen overdose has a strong, unpleasant sulfurous odor and taste, which can lead to poor compliance.
* For inhaled use, patients with reactive airway disease may experience bronchospasm; consider co-administration of a bronchodilator.
**Disclaimer:** This information is intended for healthcare professionals and is not a substitute for professional medical advice. Always consult the most current prescribing information and institutional protocols before administering any medication.
