Bacteriostatic water is sterile, nonpyrogenic water for injection with benzyl alcohol added as a preservative. The preservative keeps bacteria from growing after the vial is opened, which allows repea...
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About Bacteriostatic Water
Bacteriostatic water is sterile, nonpyrogenic water for injection with benzyl alcohol added as a preservative. The preservative keeps bacteria from growing after the vial is opened, which allows repeated withdrawals from the same multi-dose vial.[1] In research laboratories it is a standard diluent for reconstituting lyophilized peptides. Pepitiva supplies it in 3 mL and 10 mL vials.
What is in bacteriostatic water?
Water for injection, USP: sterile, nonpyrogenic water.
Benzyl alcohol, 0.9% (9 mg/mL): the bacteriostatic preservative. Some pharmaceutical presentations use 1.1%.
It contains no salts or buffers, so it is not isotonic on its own.
Bacteriostatic water versus sterile water
Sterile water for injection contains no bacteriostat or antimicrobial agent and is supplied only in single-dose containers: the unused portion is discarded.[3] Bacteriostatic water's benzyl alcohol is what makes multi-dose use possible.[1] For peptides that need a slightly acidic diluent, some protocols use acetic water instead.
For research and laboratory use.
Mechanism of Action
How the preservative works
Benzyl alcohol at 0.9% inhibits bacterial growth in the solution, which is why the product is labeled bacteriostatic rather than bactericidal: it stops growth rather than sterilizing a contaminated vial. Aseptic technique is still needed for every withdrawal.[1]
Important cautions from the official labeling
Not for use in neonates: benzyl alcohol has been associated with toxicity in newborns, including the "gasping syndrome" described in 1982.[1][2]
Not for direct intravenous use without a solute: the labeling warns that this can cause hemolysis, because plain water is hypotonic.[1]
Not for epidural or spinal procedures, and not for fluid replacement.[1]
Research Applications
Use in peptide research
Reconstituting lyophilized peptides: add the water slowly down the inside wall of the vial and swirl gently until the powder dissolves; avoid shaking. Our peptide calculator helps work out volumes and concentrations.
Multi-use stock solutions: the preservative allows several withdrawals from one vial over the course of an experiment.
Sterile water for injection containing 0.9% benzyl alcohol as a preservative. The preservative inhibits bacterial growth so the vial can be used for several withdrawals.
What are the ingredients of bacteriostatic water?
Water for injection, USP and benzyl alcohol at 0.9% (9 mg/mL). The pH is about 5.7 (range 4.5 to 7.0). It contains no salts or buffers.
What is the difference between bacteriostatic water and sterile water?
Sterile water has no preservative and comes only in single-dose containers. Bacteriostatic water contains benzyl alcohol, which allows a multi-dose vial to be opened more than once.
What is the difference between bacteriostatic water and acetic water?
Acetic water is sterile water with a small amount of acetic acid, giving a slightly acidic diluent used for certain peptides. Bacteriostatic water is close to neutral and contains benzyl alcohol. See acetic water.
How should bacteriostatic water be stored?
At controlled room temperature, 20 to 25 °C (68 to 77 °F). Do not use it unless the solution is clear and the seal intact.
Is bacteriostatic water safe for newborns?
No. The official labeling states it must not be used in neonates, because benzyl alcohol has been associated with toxicity in newborns.
Scientific References
Bacteriostatic Water for Injection, USP (Hospira, Inc.). Prescribing information, revised 08/2019. DailyMed, U.S. National Library of Medicine. Source
Gershanik J, Boecler B, Ensley H, et al. The gasping syndrome and benzyl alcohol poisoning. N Engl J Med. 1982;307(22):1384-1388. PubMed
Sterile Water for Injection, USP (Medefil, Inc.). Prescribing information. DailyMed, U.S. National Library of Medicine. Source
Sources are peer-reviewed publications indexed in PubMed and trial registrations on ClinicalTrials.gov. Each citation was checked against its PubMed record.
For research use only. Not for human consumption.
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