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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that breaks disulfide bonds in mucoproteins, reducing the viscosity of respiratory secretions. It also serves as an antidote for acetaminophen overdose by replenishing hepatic glutathione stores.
## Primary Indications
* **Acetaminophen Overdose:** Antidote.
* **Mucolytic:** Adjunct in patients with abnormal mucus secretions (e.g., COPD, cystic fibrosis, pneumonia, bronchitis).
## Adult Dosing
### Acetaminophen Overdose:
**Oral:** 140 mg/kg loading dose, followed by 70 mg/kg every 4 hours for 17 doses.
**Intravenous:** Typically administered as a 3-bag infusion protocol (e.g., 150 mg/kg over 1 hour, then 12.5 mg/kg/hr for 4 hours, then 6.25 mg/kg/hr for 16 hours). Protocols vary; consult local guidelines.
### Mucolytic:
**Nebulization:** 20% solution: 1-10 mL every 2-6 hours. 10% solution: 5-20 mL every 2-6 hours.
**Oral (Effervescent Tablets):** 200 mg 2-4 times daily.
**Oral (Solution):** 600 mg once daily or 200 mg 2-3 times daily.
## Pediatric Dosing
### Acetaminophen Overdose:
**Oral:** Same as adult dosing (140 mg/kg loading, 70 mg/kg every 4 hours for 17 doses).
**Intravenous:** Same as adult dosing; weight-based calculations are critical. Consult local guidelines.
### Mucolytic:
**Nebulization (20% solution):** 1-10 mL every 2-6 hours.
**Nebulization (10% solution):** 5-20 mL every 2-6 hours.
**Oral:** Dosing varies based on age and formulation. For effervescent tablets: typically 100-200 mg twice daily for children 2-5 years, 200 mg 2-3 times daily for children >5 years. Consult specific product labeling.
## Dose Adjustments
No specific dose adjustments are routinely recommended for hepatic or renal impairment for the mucolytic indication. For acetaminophen overdose, dose is based on weight and administration route.
## Contraindications
Hypersensitivity to acetylcysteine or any component of the formulation.
## Adverse Effects
* **Nebulized:** Bronchospasm, bronchoconstriction, stomatitis, rhinorrhea, nausea, vomiting.
* **Intravenous:** Anaphylactoid reactions (rash, pruritus, angioedema, bronchospasm, hypotension), fever, chills.
* **Oral:** Nausea, vomiting, diarrhea, abdominal pain, stomatitis.
## Key Drug Interactions
* **Activated Charcoal:** May adsorb oral acetylcysteine, reducing efficacy in acetaminophen overdose. Separate administration by at least 1 hour.
* **Nitroglycerin:** Potentiated hypotensive effects.
## Monitoring
* **Acetaminophen Overdose:** Serum acetaminophen levels, liver function tests (AST, ALT, bilirubin), prothrombin time, glucose, electrolytes, and renal function. Clinical signs of liver toxicity.
* **Mucolytic:** Respiratory status, sputum viscosity and ease of expectoration. Bronchospasm.
## Clinical Pearls
* The efficacy of acetylcysteine in acetaminophen overdose is time-dependent; administer promptly, especially if acetaminophen levels are concerning or ingestion time is unknown.
* For nebulized acetylcysteine, coadministration with a bronchodilator may be necessary to prevent or treat bronchospasm, especially in patients with reactive airway disease.
* Intravenous acetylcysteine for acetaminophen overdose requires careful monitoring for anaphylactoid reactions.
* The characteristic sulfurous odor of acetylcysteine may be unpleasant for patients.
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**Disclaimer:** This information is intended for clinical decision support and does not replace comprehensive drug information resources or a thorough review of the current prescribing information, including indications, contraindications, warnings, precautions, and adverse reactions. Always verify drug information with up-to-date resources before patient administration.
