Bacteriostatic Water
Reconstitution diluent
Sterile water containing 0.9% benzyl alcohol, used to reconstitute lyophilized research peptides for in-vitro study.
Also referenced as: BAC Water
Overview
Bacteriostatic water is sterile water for injection containing 0.9% benzyl alcohol as an antimicrobial preservative. It is a pharmaceutical-grade diluent used to reconstitute or dilute other preparations.
At a glance
What Bacteriostatic Water does
Bacteriostatic water is not a pharmacologically active agent - it is a reconstitution diluent. It is sterile water combined with 0.9% (w/v) benzyl alcohol, and its entire function is to dissolve lyophilized (freeze-dried) research peptides and other powders into a liquid so they can be measured, handled, and studied. When the diluent is added to a vial of peptide powder, the powder goes back into solution; the resulting concentration is simply the amount of peptide divided by the volume of water added.
The one functional distinction from plain sterile water is the benzyl alcohol, which acts as a bacteriostatic preservative: it inhibits the growth of bacteria in the solution. This is what allows a reconstituted multi-dose vial to be entered repeatedly and stored (typically refrigerated) over a period of days to weeks without microbial overgrowth, whereas plain sterile water offers no such protection and is intended for single use. Benzyl alcohol provides bacteriostatic (growth-inhibiting), not sterilizing, protection.
There is no invented pharmacology here: bacteriostatic water does not interact with receptors, alter metabolism, or produce biological effects of its own beyond the known considerations that benzyl alcohol should be avoided in certain sensitive settings (e.g., it is not used in neonates and is avoided by those with benzyl alcohol sensitivity). Its role is purely as a solvent/diluent that keeps the reconstituted solution usable over multiple withdrawals.
Effects reported in research
- Dissolves lyophilized (freeze-dried) peptide powder back into a measurable liquid solution - its core reconstitution role.
- Sets the working concentration of the reconstituted peptide by the volume of diluent added (functional role).
- The 0.9% benzyl alcohol inhibits bacterial growth in the solution (bacteriostatic, not sterilizing) preservation.
- Allows a multi-dose vial to be entered repeatedly and stored over days to weeks without microbial overgrowth, unlike single-use sterile water (functional role).
- Has no pharmacological activity of its own - it does not interact with receptors or alter metabolism (functional fact).
- Benzyl alcohol is generally avoided in neonatal settings and in those with benzyl alcohol sensitivity (known safety consideration).
Effects listed reflect findings reported in the research literature — many in animal or in-vitro models. Listing an effect is not a claim of efficacy or a therapeutic indication in humans.
Mechanism of action
Bacteriostatic water is sterile water combined with 0.9% (w/v) benzyl alcohol, a bacteriostatic preservative that inhibits the growth of bacteria in the solution. Chemically, it functions purely as a diluent/solvent for reconstituting lyophilized (freeze-dried) compounds; the benzyl alcohol allows the same vial to be accessed multiple times while limiting microbial contamination. It has no pharmacological activity of its own on the reconstituted compound.
Mechanistic description reflects published research-literature understanding. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
What it's studied for
Research contexts in which Bacteriostatic Water appears in the literature. Listing a research area is not a claim of efficacy or a therapeutic indication.
Key characteristics
- Sterile water preserved with 0.9% benzyl alcohol.
- Benzyl alcohol provides bacteriostatic (growth-inhibiting) preservation.
- Used solely as a diluent/solvent for reconstitution.
- Supports multiple withdrawals from a single vial.
- Has no pharmacological activity itself.
How it compares
Bacteriostatic water is a benzyl-alcohol-preserved diluent for reconstitution, distinct from acetic acid solution, which is a mild acidic solvent used to dissolve hard-to-solubilize peptides.
Handling & Stability
Liquid research solutions are typically stored cold and used within supplier-stated shelf life.
- Avoid repeated freeze-thaw cycles
- Verify supplier lot and Certificate of Analysis
- Follow institutional lab-safety protocols
Analytical & COA Concepts
Reputable research suppliers publish a third-party Certificate of Analysis per batch. Key analytical concepts referenced in COAs include:
Category Context
Bacteriostatic Water sits in the Research Solutions & Adjuncts area of the PeptiDex library.
- Entry type: Research solution / adjunct
- Browse the full library →
- Glossary of terms →
Where researchers source Bacteriostatic Water
For researchers studying Bacteriostatic Water, third-party suppliers such as Practically Natty Peptides offer research-grade material with third-party Certificates of Analysis and US-based shipping.
View research-supplier listing →
Outbound link to a third-party research supplier. Inclusion does not constitute endorsement; all editorial content is developed independently.
Frequently asked questions
What is bacteriostatic water?
Bacteriostatic water is sterile water containing a small amount of benzyl alcohol (commonly ~0.9%) as a bacteriostatic preservative. It is not a peptide or an active compound - it is a diluent used to reconstitute lyophilized peptides and other lyophilized research materials. The benzyl alcohol inhibits bacterial growth, allowing a reconstituted vial to be used over multiple withdrawals.
Why is bacteriostatic water used to reconstitute peptides?
Most research peptides are supplied as a lyophilized (freeze-dried) powder that must be dissolved into liquid before use. Bacteriostatic water is preferred over plain sterile water for multi-use vials because its benzyl alcohol preservative suppresses microbial growth, extending the usable window of the reconstituted solution when stored refrigerated. It is added slowly down the vial wall to avoid degrading fragile peptides.
How does bacteriostatic water differ from sterile water for injection?
Sterile water for injection contains no preservative and is generally intended for single use, since an opened vial has no protection against microbial growth. Bacteriostatic water adds benzyl alcohol so the same vial can be accessed multiple times over a period of days to weeks. For peptides that are sensitive to benzyl alcohol, plain sterile water or another solvent may be chosen instead.
How much bacteriostatic water is used and how is it stored?
The reconstitution volume is chosen by the researcher to reach a convenient working concentration - typically 1 to 3 mL per vial - based on the peptide mass and desired concentration. Unopened bacteriostatic water is stored at room temperature; once a peptide is reconstituted, the solution is refrigerated and protected from light. A COA/sterility statement is reasonable to expect from the supplier.
Does bacteriostatic water have any research dosing of its own?
No. It is an inert diluent/solvent and has no dose or biological activity of its own. Its only role is as the reconstitution medium for lyophilized peptides, so dosing figures do not apply to it.
Answers are educational summaries of research-literature context and do not constitute medical advice. See the Research Library, COA guide, and Storage & Handling guide for more.