What Is BAC Water?
Bac water is bacteriostatic water for injection, USP: sterile water with 0.9% benzyl alcohol added as a preservative. That preservative is what allows one vial to be drawn from repeatedly for up to 28 days rather than being discarded after a single use.
What does bacteriostatic actually mean?
Bacteriostatic means holding bacterial growth in check rather than killing bacteria outright. The distinction matters here: the benzyl alcohol is not sterilizing the vial, it is preventing anything introduced on a needle from multiplying between draws. The water was already sterile when it was sealed.
What is in the vial?
| Specification | Value |
|---|---|
| USP grade | Bacteriostatic Water for Injection, USP |
| Preservative | Benzyl alcohol 0.9% (9 mg/mL) |
| Sterility | Sterile, non-pyrogenic |
| Container | Multiple-dose glass vial |
| Closure | Rubber stopper with aluminum seal and flip-off cap |
| In-use period | 28 days after first puncture |
| Storage | 20°C to 25°C, excursions permitted to 15°C to 30°C |
| Not for use in | Neonates |
Sterile water and benzyl alcohol. Nothing else.
What is bac water used for?
It is a diluent. Something supplied as a freeze-dried powder cannot be measured or drawn until it is dissolved, and bac water is what dissolves it. The water contributes nothing beyond being a clean, preserved liquid to put the powder into.
It is not a treatment, a supplement or an active ingredient, and any description of it as one is wrong.
Why does the 28 day limit exist?
Every puncture of the stopper is an opportunity for organisms to enter. The benzyl alcohol concentration is rated to suppress growth for 28 days, so that is the window. The clock starts at the first puncture, not at the date you bought it, which is why writing that date on the label is worth the two seconds it takes.
How is it different from sterile water and saline?
| Bacteriostatic water | Sterile water | Saline | |
|---|---|---|---|
| Preservative | 0.9% benzyl alcohol | None | None (usually) |
| Contains salt | No | No | Yes, 0.9% sodium chloride |
| Doses | Multiple | One | Varies |
| Use window | 28 days | Immediate | Varies |
The full comparison is on bac water vs sterile water.
Where do you get it?
Not from a supermarket shelf. It is a prescription product, so it comes from an online supplier, a pharmacy counter, or a licensed distributor. Retailer by retailer, that is covered on where to buy bac water.
Frequently Asked Questions
- What does bac water stand for?
- Bac water is short for bacteriostatic water for injection, USP. Bacteriostatic means it suppresses bacterial growth rather than killing bacteria outright, which is the job of the 0.9% benzyl alcohol it contains.
- What is bac water used for?
- Bac water is used as a diluent, dissolving or diluting another substance supplied as a powder. It has no effect of its own and is not a treatment for any condition.
- Is bac water safe?
- Bacteriostatic water is an FDA-approved product manufactured to a USP monograph. It is not for use in neonates because of its benzyl alcohol content, a restriction printed on every genuine vial.
- What is in bac water?
- Bac water contains sterile water for injection and benzyl alcohol at 0.9%, which is 9 mg per mL. There is nothing else in the vial.
- Why is bac water called multiple-dose?
- It is called multiple-dose because the benzyl alcohol lets the stopper be punctured repeatedly for up to 28 days. Vials without a preservative are single-dose and are discarded after one use.
- Can bac water expire?
- Yes, in two ways. Unopened it expires on the date printed on the vial. Once punctured it lasts 28 days regardless of that date, and the earlier of the two is the one that applies.
Important notices
Bacteriostatic water for injection, USP is a diluent used to dissolve or dilute another substance. It is not a treatment for any condition and makes no claim to be one. It contains benzyl alcohol and is not for use in neonates. Discard the vial 28 days after the first puncture.