Bacteriostatic vs sterile water
These two vials look identical. They are not interchangeable — and the mix-up either wastes a vial or leaves you reusing something that was never meant to be reused.
The one difference that matters
Bacteriostatic water contains 0.9% benzyl alcohol as a preservative. That's what allows a vial to be punctured repeatedly — standard practice treats it as usable for roughly 28 days once opened, kept refrigerated.
Sterile water for injection has no preservative. It's single-use: one puncture, then it's done. Leaving it for a second draw isn't a gray area — it's an open, unpreserved vial sitting at room or fridge temperature.
Why it matters
Neither choice has anything to do with what's being reconstituted. It's entirely about how many times the vial gets entered. Multi-use needs a preservative. Single-use doesn't have one. That's the whole rule.
- Bacteriostatic water → multi-dose, ~28 days refrigerated once opened, 0.9% benzyl alcohol
- Sterile water → single-use, no preservative, discard after one draw
- Neither is interchangeable with the other regardless of what's being mixed
Looking for bacteriostatic or sterile water?