Bacteriostatic Water in Canada — Research Guide

What is bacteriostatic water?

Bacteriostatic water for injection is sterile, non-pyrogenic water preserved with 0.9% benzyl alcohol (9 mg per mL). It is the standard diluent that research laboratories and compounding pharmacies use to dissolve lyophilised (freeze-dried) peptides and other powdered compounds that are unstable once hydrated. Unlike plain sterile water, it can be punctured multiple times and used across roughly a 28-day in-use window, which is essential for a researcher working through a multi-milligram peptide vial over several weeks.

Bacteriostatic water is supplied in 10 mL, 20 mL, or 30 mL glass vials with a rubber stopper. It is colourless, clear, and has a faint odour from the benzyl alcohol.

Why 0.9% benzyl alcohol matters

Benzyl alcohol at 0.9% (w/v) is a well-characterised bacteriostatic preservative. Its role is narrow but important: after the first needle puncture, any bacteria introduced through the stopper are held in check rather than allowed to multiply in the vial. This is the entire reason bac water exists as a separate product from plain sterile water — the preservative is what permits multi-dose reconstitution.

Benzyl alcohol is generally regarded as safe at this concentration in adult research contexts, but it is not appropriate for neonates (the historical "gasping syndrome" association) and is contraindicated in certain compounded formulations. Researchers should read the diluent label before use.

Bac water vs sterile water vs saline

Saline is isotonic but unpreserved, so it offers no reuse advantage for multi-week work. Sterile water is unpreserved and must be discarded after first puncture. For multi-use peptide reconstitution, bacteriostatic water is the diluent of choice.

Reconstitution procedure

The six-step procedure in the HowTo block above walks through a safe reconstitution: sanitise the stoppers, draw the calculated volume, inject slowly down the vial wall so the stream does not impact the lyophilised cake directly, swirl gently (never shake), label the vial with the date and concentration, and refrigerate. For peptide-specific notes — target concentration, syringe unit conversions, and stability windows — see the related reconstitution guide.

Storage and shelf life of reconstituted peptides

Once a lyophilised peptide is reconstituted, its stability clock starts. General handling guidance:

• Refrigerate at 2–8°C, upright, away from light.
• Do not freeze a reconstituted vial — ice crystal formation can cleave peptide bonds and aggregate the sample.
• Typical in-use window for reconstituted research peptides is 2–4 weeks, though this varies by compound. Stable, well-characterised peptides (e.g. some GLP-1 analogues) can extend further; sensitive ones (e.g. some growth-factor mimetics) degrade faster.
• Discard the vial if the solution becomes cloudy, develops particulates, or changes colour.

The underlying bac water vial itself, once punctured, is labelled for roughly 28 days of use and should be discarded after that window regardless of remaining volume.

Where to buy bacteriostatic water in Canada

In Canada, bacteriostatic water is typically sourced from compounding pharmacies or from research-supply vendors. Retail availability is inconsistent — it is not a shelf item at consumer pharmacies the way it can be in some other jurisdictions. OVIOPEPTIDES stocks bacteriostatic water in research-grade vials for Canadian laboratories alongside the lyophilised peptides it is paired with: see bacteriostatic water.

For the regulatory framing that applies to every research reagent sold on this site, including bac water and the peptides it reconstitutes, read our peptides in Canada guide.