Bacteriostatic water

Also known as: bac water · bacwater · bac-water · bw

Sterile water containing about 0.9% benzyl alcohol as a preservative, allowing a vial to be entered more than once.

In plain terms

The benzyl alcohol inhibits bacterial growth, which is what makes multi-dose use possible. Plain sterile water has no preservative and is single-use: once the stopper is pierced, anything introduced will grow.

Benzyl alcohol is not appropriate for everyone — it is contraindicated in neonates, and some people react to it. It is also why bacteriostatic water is not used for very large-volume injections.

Guides that use this term

How to reconstitute a peptide (and the maths behind it)

How much bacteriostatic water to add, why the volume changes what a “unit” means, and the handling mistakes that silently degrade a peptide. With the arithmetic worked through.

How to store peptides: fridge, freezer, travel and heat

Lyophilised powder, reconstituted solution, and what actually happens when a vial gets warm. Storage rules, travel guidance, and why a degraded peptide looks exactly like a good one.

Educational reference only. Pepperz does not provide medical advice, diagnosis, treatment, prescribing guidance, or dosing recommendations.