Bacteriostatic water is a specialized form of sterile water that plays a significant role in medical and laboratory settings. It is primarily used as a diluent, meaning it helps dissolve or dilute various medications, particularly those intended for injection. Understanding its effective lifespan and safe use is important. This article explores the factors contributing to its viability and guidelines for proper handling.
What Gives Bacteriostatic Water Its Longevity?
Bacteriostatic water distinguishes itself from plain sterile water through the inclusion of an ingredient: benzyl alcohol. This compound is present in a small concentration, 0.9%, and acts as a bacteriostatic agent. The term “bacteriostatic” indicates its ability to inhibit the growth and reproduction of bacteria within the vial.
The presence of benzyl alcohol allows bacteriostatic water to be a multi-dose solution. Unlike sterile water, which must be used immediately after opening due to contamination risks, bacteriostatic water can be accessed repeatedly without rapidly compromising its integrity. This preservative action helps maintain the solution’s integrity even after the vial stopper has been punctured.
Understanding Bacteriostatic Water’s Shelf Life
The longevity of bacteriostatic water depends on whether its vial remains unopened or has been accessed. An unopened vial has a shelf life of two to three years from its manufacturing date. The expiration date is printed on the vial and should always be checked before use for quality.
Once a multi-dose vial of bacteriostatic water is opened or punctured, a different timeframe applies. The guideline is to use it within 28 days. This “28-day rule” exists because, despite benzyl alcohol, the risk of contamination increases with each withdrawal from the vial. Over time, the effectiveness of benzyl alcohol as a preservative can diminish, potentially allowing bacterial growth not visible to the naked eye.
Ensuring Safe Use and Storage
To maximize the effective life and ensure the safety of bacteriostatic water, proper storage and handling are necessary. Unopened vials should be stored at a consistent room temperature, between 20°C to 25°C (68°F to 77°F). Also, keep vials away from direct sunlight or extreme heat, and avoid freezing, which can compromise the water’s sterile integrity.
Once a vial has been opened, label it with the date of first use. While refrigeration is not always required, storing opened vials in a cool, dry place is recommended. Before each use, visually inspect the water for any signs of degradation, such as cloudiness, discoloration, or visible particles. Any vial showing these signs or that has been open for longer than 28 days should be discarded to prevent potential health risks.