The core difference: salt
The two products are easy to confuse because they share a name pattern and the same preservative. The difference is the salt:
| Property | Bacteriostatic water | Bacteriostatic 0.9% sodium chloride |
|---|---|---|
| Base | Water for injection | 0.9% saline (isotonic) |
| Sodium chloride | None | 0.9% (9 mg/mL) |
| Preservative | 0.9% benzyl alcohol | 0.9% benzyl alcohol |
| Tonicity | Hypotonic | Isotonic |
| Multi-dose? | Yes | Yes |
When the difference matters
Whether a workflow calls for plain preserved water or preserved isotonic saline depends on the material being reconstituted and the protocol in use. The salt in bacteriostatic sodium chloride changes the tonicity of the resulting solution, which can matter for some preparations and be irrelevant for others. The choice is dictated by your protocol — the two are not freely interchangeable just because both are preserved and multi-dose.
What they have in common
Both products rely on 0.9% benzyl alcohol as the bacteriostatic preservative, which is what makes both available in repeated-entry multi-dose vials. For a deeper look at how the preservative works, see benzyl alcohol in bacteriostatic water.
Which do most researchers buy?
Bacteriostatic water is the more commonly stocked of the two as a general-purpose research diluent. We supply 10 mL multi-dose bacteriostatic water — sterile-filtered, 0.9% benzyl alcohol, documented to the lot. See the product. Always confirm your protocol specifies water versus saline before ordering.
Frequently asked questions
What is the difference between bacteriostatic water and bacteriostatic sodium chloride?
Bacteriostatic water is preserved water with no salt; bacteriostatic sodium chloride is preserved 0.9% saline, which is isotonic. Both use 0.9% benzyl alcohol as the preservative, but the salt content makes them non-interchangeable.
Are bacteriostatic water and bacteriostatic saline interchangeable?
No. The salt in bacteriostatic sodium chloride changes the tonicity of the resulting solution. Which one a workflow requires is dictated by the protocol and the material being reconstituted.
Do both contain benzyl alcohol?
Yes. Both contain 0.9% benzyl alcohol as the bacteriostatic preservative, which is what makes each available as a repeated-entry multi-dose vial.