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# Acetylcysteine
## Overview
Acetylcysteine is a mucolytic agent that works by breaking disulfide bonds in mucoproteins, thus decreasing the viscosity of mucus. It is also the antidote for acetaminophen overdose.
## Primary Indications
* **Acetaminophen Overdose:** Treatment of acetaminophen overdose.
* **Mucolytic:** Adjunct therapy in patients with abnormal mucus secretions due to chronic bronchopulmonary disease (e.g., bronchitis, emphysema, cystic fibrosis).
## Adult Dosing
### Acetaminophen Overdose
* **IV:** Typically initiated with a loading dose of 150 mg/kg, followed by an infusion of 12.5 mg/kg/hour for 4 hours, then 6.25 mg/kg/hour for 16 hours. Total treatment duration is typically 20 hours. Doses may be adjusted based on acetaminophen levels and clinical status. Higher initial bolus doses may be used in severe overdose or if hypotension occurs.
* **Oral:** Typically initiated with a loading dose of 140 mg/kg, followed by 70 mg/kg every 4 hours for 17 doses.
* **Maximum Dose:** Not explicitly defined for the infusion, but based on the 150 mg/kg loading dose and subsequent infusions, it would be substantial in a large adult.
### Mucolytic
* **Inhalation (Nebulizer):** 1-10 mL of a 10% or 20% solution every 2-6 hours as needed.
* **Inhalation (Direct Instillation):** 1-10 mL of a 10% or 20% solution.
* **Oral:** 200 mg twice daily to 600 mg three times daily.
## Pediatric Dosing
### Acetaminophen Overdose
* **IV:** Same as adult dosing: 150 mg/kg loading dose, then 12.5 mg/kg/hour for 4 hours, then 6.25 mg/kg/hour for 16 hours. Maximum initial dose should not exceed 150 mg/kg.
* **Oral:** Same as adult dosing: 140 mg/kg loading dose, then 70 mg/kg every 4 hours for 17 doses.
### Mucolytic
* **Inhalation (Nebulizer):**
* Ages 1 month to 18 years: 1-10 mL of a 10% or 20% solution every 2-6 hours as needed.
* **Oral:** Dosing varies and is often based on weight. Commonly used doses include 50-100 mg 3-4 times daily for younger children, and up to 200 mg twice daily for older children and adolescents. Specific dosing for pediatrics often relies on institutional protocols.
## Dose Adjustments
* **Renal Impairment:** No specific dose adjustments are typically recommended, but caution is advised due to potential for increased adverse effects.
* **Hepatic Impairment:** No specific dose adjustments are typically recommended, but caution is advised.
## Contraindications
* Known hypersensitivity to acetylcysteine or any component of the formulation.
* Active bronchospasm (for inhaled formulations).
## Adverse Effects
* **Common (Inhaled):** Bronchospasm, bronchoconstriction, nausea, vomiting, stomatitis, rhinorrhea, drowsiness.
* **Common (IV for overdose):** Anaphylactoid reactions (rash, urticaria, pruritus, flushing, angioedema), nausea, vomiting, fever, tachycardia.
* **Common (Oral):** Nausea, vomiting, diarrhea, rash.
## Key Drug Interactions
* **Activated Charcoal:** May reduce the absorption of oral acetylcysteine if given concurrently. Separate administration.
* **Nitroglycerin:** May potentiate the vasodilatory effects of nitroglycerin, leading to hypotension and severe headache. Monitor blood pressure and heart rate.
## Monitoring
* **Acetaminophen Overdose:**
* Acetaminophen plasma levels.
* Liver function tests (ALT, AST, bilirubin, INR).
* Renal function (BUN, creatinine).
* Electrolytes.
* Blood glucose (especially with IV infusion).
* Clinical signs of toxicity (e.g., encephalopathy, coagulopathy).
* Vital signs, especially blood pressure and heart rate due to risk of anaphylactoid reaction.
* **Mucolytic:**
* Respiratory status (e.g., breath sounds, sputum production, oxygen saturation).
* Bronchospasm.
## Clinical Pearls
* For IV administration in acetaminophen overdose, hydration is crucial.
* Anaphylactoid reactions are common with IV acetylcysteine and can be severe but are usually manageable with antihistamines and slowed infusion.
* Oral acetylcysteine is less effective than IV for acetaminophen overdose, especially if presentation is delayed, but may be used if IV is not feasible.
* When nebulizing, dilute with sterile water or saline to a minimum of 10% concentration if a 20% solution is used, to minimize airway irritation.
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*Disclaimer: This information is intended for clinical use and does not replace the need to consult the official prescribing information for the specific product being used, as well as institutional protocols. Dosing and recommendations may vary.*
