Can acetylcysteine (N-acetylcysteine) 20% be diluted in water?

Can Acetylcysteine 20% Be Diluted in Water?

Yes, acetylcysteine 20% solution can be diluted in water—the FDA-approved drug label explicitly states that "the 20% solution may be diluted to a lesser concentration with either Sodium Chloride for Injection, Sodium Chloride for Inhalation, Sterile Water for Injection, or Sterile Water for Inhalation." 1

FDA-Approved Dilution Guidelines

The official FDA labeling provides clear direction on dilution practices:

• The 20% acetylcysteine solution may be diluted with Sterile Water for Injection or Sterile Water for Inhalation to achieve lower concentrations 1
• For oral administration as an acetaminophen antidote, the 20% solution should be diluted to a final concentration of 5% using diet cola or other diet soft drinks (though water may be used if administered via gastric or Miller-Abbott tube) 1
• For nebulization/inhalation use, the 20% solution can be diluted with sterile water to appropriate concentrations 1

Specific Dilution Protocols by Route

Oral Administration (Acetaminophen Overdose)

• Dilute 20% solution to 5% concentration using diet soft drinks as the preferred diluent, or water if using gastric tube administration 1
• Freshly prepared dilutions should be utilized within one hour 1
• Loading dose: 140 mg/kg, followed by maintenance doses of 70 mg/kg every 4 hours for 17 total doses 1

Inhalation/Nebulization Use

• 1-10 mL of 20% solution (or 2-20 mL of 10% solution) may be given every 2-6 hours when nebulized 1
• The solution may be diluted with sterile water, sodium chloride injection, or sodium chloride inhalation solution 1

Intravenous Preparation (Off-Label in US)

• For IV use, 150 mL of 20% solution can be added to 1 L of 5% dextrose in water (D5W) to create a 2.6% solution 2
• This preparation remains stable for at least 60 hours and is free from bacterial contamination 2
• A simplified protocol uses 30 g in 1 L D5W with 150 mg/kg loading dose over 1 hour, followed by 14 mg/kg/hour for 20 hours 3

Important Stability and Storage Considerations

Acetylcysteine does not contain antimicrobial agents, requiring careful handling to minimize contamination 1:

• Opened, undiluted vials can be refrigerated and used within 96 hours 1
• Freshly prepared oral dilutions should be used within 1 hour 1
• IV preparations in D5W remain stable for 60 hours at room temperature 2

Common Pitfalls and Caveats

• Do not use reactive materials (iron, copper, rubber) in nebulization equipment; use glass, plastic, aluminum, or stainless steel instead 1
• Acetylcysteine is NOT approved for parenteral injection in the United States—only oral and inhalation routes are FDA-approved 1
• If activated charcoal has been given for acetaminophen overdose, lavage before administering acetylcysteine, as charcoal can adsorb up to 96% of the drug 1, 4
• Water dilution for oral use is less palatable than diet soft drinks; Fresca has been shown to significantly reduce offensive odor and taste compared to water, chocolate milk, or cranberry juice 5