Bacteriostatic water is a specialized solution primarily used in medical and laboratory settings as a diluent. Its main purpose is to prepare medications requiring reconstitution or dilution, ensuring their stability and safety for injection. This water’s unique composition allows its use where standard sterile water might not be suitable.
What Makes Water Bacteriostatic?
Bacteriostatic water consists of sterile water for injection combined with a bacteriostatic agent, typically 0.9% benzyl alcohol (BnOH). The sterile water component is purified, with bacteria removed through processes like filtration or heat.
The term “bacteriostatic” signifies that benzyl alcohol inhibits bacterial growth and reproduction. It prevents bacteria from multiplying rather than killing them. This property allows the solution to maintain its integrity longer than plain sterile water, which lacks a preservative.
Benzyl alcohol disrupts the cell membrane integrity of microorganisms, hindering their growth. This preservative effect prevents bacterial growth in sterile water once exposed to air or punctured.
Key Applications of Bacteriostatic Water
The primary application of bacteriostatic water is in reconstituting or diluting powdered medications. Many injectable drugs, such as hormones, peptides, or other compounds, are manufactured as lyophilized powders that require a liquid for administration. Bacteriostatic water provides a suitable and stable vehicle for this process.
Its bacteriostatic property is important for multi-dose vials. It helps maintain the sterility of the solution after the vial has been punctured, allowing for safe repeated withdrawals over a specified period, typically up to 28 days. Without the preservative, a multi-dose vial of sterile water would be compromised after the first entry.
Bacteriostatic water is designed for parenteral (injection) use, such as intramuscular, intravenous, or subcutaneous injections. It is commonly used for medications like insulin, vaccines, and human chorionic gonadotropin (HCG). Bacteriostatic water is not intended for oral consumption, wound cleaning, or direct injection without a dissolved substance, as this can cause adverse effects like hemolysis.
Proper Handling and Storage
Proper handling and storage are important for maintaining the sterility and effectiveness of bacteriostatic water. When preparing solutions, sterile technique should be followed to prevent contamination. This includes using a new, sterile syringe and needle for each withdrawal from the vial.
Unopened vials of bacteriostatic water have a shelf life of two to three years when stored correctly. They should be kept in a cool, dry place, away from direct light and heat, ideally at room temperature between 15°C and 30°C. Avoiding freezing is important, as it can compromise the water’s sterile integrity.
Once a vial of bacteriostatic water has been punctured, its shelf life is significantly reduced. It should be used within 28 days. After this period, the preservative may lose its efficacy, increasing the risk of bacterial growth. Label the vial with the date of first use and discard any unused portion after 28 days or if contamination signs are visible, such as cloudiness, discoloration, or particulate matter. Bacteriostatic water should only be used under medical guidance and for its intended purpose.