Bacteriostatic water is sterile water that contains a very small amount of benzyl alcohol as a preservative. It is commonly used to reconstitute medications, dilute injectables, and prepare solutions for injection. But how long does bacteriostatic water actually last for once opened or mixed with other components? Here’s a detailed look at the shelf life and expiration guidelines for bacteriostatic water.
What is Bacteriostatic Water?
Bacteriostatic water, often abbreviated as BW, BST, or BAC, is sterile water for injection that contains 0.9% benzyl alcohol added as a preservative and bacteriostatic agent. Benzyl alcohol prevents the growth of mold, bacteria, and fungi that could contaminate the solution.
Some key facts about bacteriostatic water:
- It contains 0.9% benzyl alcohol as a preservative
- It is sterile and pyrogen-free
- It is for single use only
- It is commonly used to reconstitute medications, dilute injectables, and prepare solutions for subcutaneous injection
- It is available in vials, ampules, and syringes in various volumes like 10ml, 20ml, 30ml
- It does not contain any active pharmaceutical ingredients or medications
Bacteriostatic water is not meant for direct injection or intravenous infusion. It is used primarily as a diluent or reconstituting agent. The low concentration of benzyl alcohol is bacteriostatic, not bactericidal, meaning it inhibits further growth of organisms but does not fully sterilize the solution.
How is Bacteriostatic Water Used?
The main uses of bacteriostatic water include:
- Reconstituting lyophilized or freeze-dried medications: Bacteriostatic water is commonly used to reconstitute medications like peptides, hormones, or antibiotics that come in powder form inside vials. The powder is mixed with bacteriostatic water to create an injectable solution.
- Diluting medications or drugs: BW can be used to dilute concentrated medications to the desired concentration for subcutaneous injection.
- Preparing solutions for subcutaneous injection: Mixed solutions can be prepared for subcutaneous injections using bacteriostatic water as the sterile diluent.
- Maintaining moisture in vials: Some multi-use vials need moisture to maintain stability of the dried medication between uses. Bacteriostatic water can help keep them moist.
Using sterile bacteriostatic water as a diluent maintains sterility and prevents the growth of bacteria that could contaminate the solutions. This helps prolong the shelf life of compounded sterile preparations.
How Long Does Unopened Bacteriostatic Water Last?
Unopened, sealed vials of bacteriostatic water can typically last 12-60 months from the date of manufacture if stored properly:
- In the unopened, original container: 12-24 months
- Refrigerated at 2°C to 8°C: 24-36 months
- Frozen at -10°C to -20°C: Up to 60 months
The exact shelf life depends on the manufacturer and the storage conditions. Refrigerating or freezing helps prolong the shelf life once opened. Always check the expiration date on the packaging.
Once bacteriostatic water vials are punctured and opened, they should be used immediately. Open vials cannot be stored for later use due to lack of sterility.
How Long Does Opened Bacteriostatic Water Last?
Once bacteriostatic water vials are opened or punctured, the contents are no longer sterile. Opened vials of bacteriostatic water have very short shelf lives.
According to USP guidelines, opened containers of sterile preparations compounded from sterile ingredients like bacteriostatic water should be used within the following time frames:
- At room temperature: Use within 48 hours
- Refrigerated: Use within 14 days
However, best practice is to use opened vials of bacteriostatic water immediately. Do not store opened vials for later use due to contamination risks.
If some product remains after single use, it must be discarded and not used for subsequent preparations.
Does Adding Bacteriostatic Water Extend Shelf Life?
Adding bacteriostatic water to reconstitute or dilute medications does not extend their shelf life. The shelf life of the reconstituted or diluted medication depends on the stability of the drug itself.
For example, reconstituted peptides and proteins in bacteriostatic water are often only stable for 24-72 hours refrigerated. Some other medications reconstituted with bacteriostatic water may be stable for weeks or months if stored properly. Always follow the manufacturer or compounding pharmacy’s instructions for storage and shelf life.
While bacteriostatic water helps prevent microbial growth in solutions, it does not prevent chemical degradation of the active drug or damage from light exposure.
How Long Does Reconstituted Bacteriostatic Water Last?
Reconstituted bacteriostatic water refers to solutions prepared by mixing bacteriostatic water with other sterile components like medications, diluents or solvents.
The shelf life of reconstituted solutions depends on the drug stability. General guidelines include:
- Peptides reconstituted with bacteriostatic water: 24-72 hours refrigerated
- Steroid solutions: 4-6 weeks refrigerated
- Antibiotic solutions: 1-2 weeks refrigerated
More complex sterile preparations should be assigned beyond-use dates based on drug stability testing data when available. Preparations containing preservatives like benzyl alcohol may have longer shelf lives. Follow instructions from the drug manufacturer or compounding pharmacy.
Does Refrigeration Extend the Shelf Life?
Yes, refrigeration can help extend the shelf life of bacteriostatic water solutions. According to USP guidelines:
- Unopened bacteriostatic water vials can be stored for 24-36 months refrigerated.
- Opened bacteriostatic water vials can be stored up to 14 days refrigerated.
- Reconstituted medications and solutions may have much longer refrigerated shelf lives depending on the drug.
Refrigeration helps slow chemical degradation and microbial growth. However, freezing is not recommended for most solutions after reconstitution or dilution as it could negatively impact drug stability.
What Happens if Bacteriostatic Water Expires?
Expired bacteriostatic water may not maintain sterility or effectiveness as a diluent. Using expired bacteriostatic water to reconstitute or dilute medications could increase the risk of contamination.
If bacteriostatic water is expired, it’s best practice to discard it and use a fresh, unexpired vial. Do not use expired vials for reconstitution or dilution purposes.
Unopened expired vials that were stored properly may still be physically sterile for some time. However, there is no assurance the benzyl alcohol remains effective at inhibiting microbial growth. To be safe, avoid using any bacteriostatic water vials beyond the manufacturer’s labeled expiration date.
Can You Extend the Expiration Date?
No, the expiration date on the manufacturer’s label should always be followed. There is no reliable way to extend the expiration date of bacteriostatic water at home.
The benzyl alcohol preservative may lose effectiveness over time, especially in opened vials. While unopened vials stored in the freezer may technically maintain sterility longer, there is no assurance. Play it safe and discard vials after the labeled expiration date.
What are Signs of Contamination?
Signs that opened bacteriostatic water vials may be contaminated and should be discarded include:
- Cloudiness
- Particulate matter
- Discoloration
- Signs of microbial growth
- Fizzing or bubbling
- Strange odors
Opened vials are not sterile and easily become contaminated. Always inspect vials carefully before use. When in doubt, throw it out.
Can Contaminated Bacteriostatic Water Be Saved?
No, if bacteriostatic water shows any signs of contamination it should be discarded. There is no safe way to “re-sterilize” or save contaminated vials.
Attempting to sterilize contaminated vials at home could make things worse. Methods like reheating or freezing do not reliably kill all microbes or remove waste products. The only safe approach is to discard the contaminated vial to prevent injection of pathogens.
Proper Storage and Handling
To help bacteriostatic water maintain effectiveness and minimize contamination risks:
- Check expiration dates and do not use expired vials
- Store unopened vials properly, either at room temperature, refrigerated, or frozen
- Keep packaging intact until ready to use
- Do not use opened vials – discard them immediately after single use
- Use clean needles each time and avoid touching puncture sites
- Inspect vials for signs of contamination before use
- Follow aseptic technique when preparing solutions
- Label solutions clearly and store refrigerated
- Follow instructions for max storage times and beyond use dating
Adhering to sterile procedures helps prevent bacteriostatic water contamination and maintain appropriate shelf lives. When in doubt, it’s always best to play it safe and start with a fresh, unexpired vial.
Key Takeaways
Here are some key takeaways on the shelf life and expiration of bacteriostatic water:
- Unopened vials last 12-60 months depending on storage conditions
- Opened vials should be used immediately and discarded after single use
- Adding bacteriostatic water alone does not extend the shelf life of medications
- Reconstituted medications have variable shelf lives depending on the drug
- Refrigeration can help prolong the shelf life of solutions
- Discard expired, contaminated, or compromised bacteriostatic water
- Always adhere to sterile procedures when handling bacteriostatic water
Following the manufacturer’s instructions, USP guidelines, and best practices for sterile preparations are essential for maintaining appropriate beyond-use dating and minimizing contamination risks when using bacteriostatic water.
The Bottom Line
Bacteriostatic water is a sterile diluent that contains benzyl alcohol as a preservative. Unopened, sealed vials can typically last around 2 years at room temperature when stored properly. However, once bacteriostatic water vials are opened, they should be used immediately and not stored for later use.
While bacteriostatic water helps prevent microbial growth, the shelf life of reconstituted or diluted medications depends on the stability of the active drug. Refrigeration and aseptic sterile technique helps prolong the shelf life of bacteriostatic water solutions once opened. However, contaminated vials should always be discarded. Following manufacturer guidelines and best practices for handling sterile preparations is key for safe and appropriate use.
