Both bacteriostatic water and sterile water for injection are purified water, but they behave differently once a vial is opened, and that difference is the whole point.
Sterile water
Sterile water for injection is purified water with nothing added. It is single-use by design: once the seal is broken there is no preservative to stop microbial growth, so any unused portion is discarded.
Bacteriostatic water
Bacteriostatic water is sterile water with about 0.9% benzyl alcohol added as a preservative. "Bacteriostatic" means the additive inhibits the growth of bacteria. Because of that preservative, a multi-dose vial can be entered more than once and used over a period of time rather than discarded after a single entry. The genuine Pfizer Hospira product we carry is a 30 ml multi-dose vial: see the bacteriostatic water listing.
Why the preservative matters for multi-dose use
The benzyl alcohol is what allows repeated entry into the same vial over time. A common laboratory convention is to discard a multi-dose vial 28 days after it is first entered, and to keep it at controlled room temperature in between. Always follow the manufacturer labeling for the specific product you have.
Storage at a glance
- Store at controlled room temperature, 68 to 77°F (20 to 25°C).
- Do not freeze.
- Keep the vial sealed and out of direct sunlight until first use.
- After first entry, follow standard practice on discard timing per the product labeling.
Choosing between them
For a single reconstitution that will be used at once, sterile water is sufficient. For work where a vial of diluent is entered more than once over days, the preservative in bacteriostatic water is what makes multi-dose use practical. Our reconstitution calculator handles the mixing math either way.
PreppinPeppers sells laboratory hardware and consumables for research, educational, and demonstration use only. This article is general educational information about equipment and does not describe, recommend, or instruct the use of any peptide or other substance in humans or animals. Nothing here is medical advice.