Bacteriostatic Water for Injection (BWFI) is a specialized liquid used in medical settings to prepare powdered medications for injection. It acts as a reliable diluent, allowing medical professionals to dissolve or reconstitute certain drugs into an injectable form. BWFI contains an additive that maintains the solution’s integrity, making it suitable for applications requiring multi-use stability.
Defining Bacteriostatic Water
Bacteriostatic Water for Injection is Sterile Water for Injection combined with a specific preservative agent. The solution is prepared to be sterile and non-pyrogenic, meaning it is free from microorganisms and fever-inducing substances. The defining component is the bacteriostatic agent, typically Benzyl Alcohol (BA).
The term “bacteriostatic” describes the preservative’s action: inhibiting the growth and reproduction of bacteria rather than killing them outright. This differs from a bactericidal agent, which actively destroys bacteria. Benzyl Alcohol is most commonly present at a concentration of 0.9% (9 mg/mL), which prevents microbial proliferation.
Why This Water is Necessary
The primary reason for using BWFI is to support the safe, repeated use of a medication vial. Many injectable drugs are supplied as a sterile powder and must be reconstituted with a diluent before administration. Using plain Sterile Water for Injection requires the entire vial of reconstituted medication to be used or discarded immediately after the first dose is drawn.
This immediate disposal is necessary because puncturing the rubber stopper compromises the sterility of the remaining liquid, risking bacterial contamination. BWFI solves this by using the Benzyl Alcohol preservative to maintain the solution’s integrity after repeated needle punctures. The Benzyl Alcohol inhibits any bacteria introduced during subsequent withdrawals, allowing the vial to be accessed multiple times. This makes BWFI appropriate for medications administered in small, multiple doses over time.
Safe Handling and Storage
Proper handling and storage ensure the continued safety and efficacy of the reconstituted medication. Once BWFI is used to reconstitute a drug, the shelf life of the new solution is significantly limited. The general guideline established by the United States Pharmacopeia (USP) for multi-dose vials is to discard the reconstituted product after 28 days. This limit is imposed because the Benzyl Alcohol’s preservative action diminishes over time and repeated exposure, increasing the risk of contamination.
A major safety restriction concerns the use of BWFI in newborns and infants. Benzyl Alcohol has been linked to severe toxicity, known as “Gasping Syndrome,” particularly in premature neonates. This condition is characterized by metabolic acidosis, respiratory distress, and central nervous system depression. Infants cannot efficiently break down Benzyl Alcohol due to immature metabolic pathways, leading to its accumulation. Therefore, only preservative-free Sterile Water for Injection should be used for preparing medications for neonates.
Unopened BWFI vials should be stored in a cool, dark environment, ideally at controlled room temperature, which is typically between 68 and 77 degrees Fahrenheit. Protection from light and extreme temperatures helps prevent the premature degradation of the Benzyl Alcohol preservative, extending the shelf life of the unopened product. After reconstitution, the specific storage conditions and temperature requirements for the final drug solution must always adhere to the drug manufacturer’s instructions.