Comparison · water or sodium chloride
Bacteriostatic Saline vs Bacteriostatic Water
Bacteriostatic saline is 0.9% sodium chloride with the same benzyl alcohol preservative as bacteriostatic water. Same preservative, same multiple-dose vial, different base: one is isotonic salt water, the other is plain water.
Bacteriostatic 0.9% Sodium Chloride Injection, USP contains 9 mg of sodium chloride and 9 mg of benzyl alcohol in every millilitre. It is isotonic, multiple-dose and labelled only as a diluent for drugs given by injection. They are not interchangeable: the label of the drug being prepared names which one to use.
What bacteriostatic saline is
Hospira’s label: “a sterile, nonpyrogenic, isotonic solution of sodium chloride in water for injection. Each milliliter (mL) contains sodium chloride 9 mg and 0.9% (9 mg/mL) benzyl alcohol added as a bacteriostatic preservative.”
- Base
- Sodium chloride 9 mg/mL in water for injection
- Preservative
- Benzyl alcohol 0.9% (9 mg/mL)
- Tonicity
- Isotonic
- pH
- 5.0 (range 4.5 to 7.0); may contain hydrochloric acid for adjustment
- Container
- Multiple-dose plastic Fliptop vials: 10, 20 and 30 mL
- Storage
- 20 to 25 °C (68 to 77 °F)
- Indication
- Diluting or dissolving drugs for IV, IM or subcutaneous injection
Saline vs water
| Bacteriostatic saline | Bacteriostatic water | |
|---|---|---|
| Base | 0.9% sodium chloride (9 mg/mL) | Water for injection only |
| Preservative | Benzyl alcohol 0.9% | Benzyl alcohol 0.9% (1.1% in one glass vial) |
| Tonicity | Isotonic | Must be “made approximately isotonic prior to use” |
| pH on the Hospira label | 5.0 (4.5 to 7.0) | 5.7 (4.5 to 7.0) |
| Container | Multiple-dose, 10, 20 and 30 mL | Multiple-dose, 30 mL |
| Neonates | Not used | Not used |
| Status | Rx only | Rx only |
The sodium chloride is the whole difference. Some drugs are stable in salt water and some are not, and some dissolve better in one than the other. That is why both labels hand the decision to “the manufacturer’s instructions for choice of vehicle”. A drug label that names bacteriostatic water does not make saline an acceptable substitute, and the reverse is also true.
Sodium chloride for injection
“Sodium chloride for injection” is the wider family: sterile 0.9% sodium chloride solutions sold in vials, flushes and bags, most of them preservative-free. Bacteriostatic saline is the one member with benzyl alcohol added, and the label draws the line between them twice:
- “Preservative-free Sodium Chloride Injection should be used for flushing intravascular catheters.”
- “Where a sodium chloride solution is required for preparing or diluting medications for use in neonates, only preservative-free Sodium Chloride Injection should be used.”
So a vial labelled “0.9% Sodium Chloride Injection” without the word “Bacteriostatic” contains no benzyl alcohol, and is not a multiple-dose product unless its own label says so.
What the label rules out
The restrictions match those on bacteriostatic water, with one addition for saline:
- Not for neonates: “Due to the potential toxicity of benzyl alcohol in neonates, solutions containing benzyl alcohol must not be used in this patient population.”
- Not “for fluid or sodium chloride replacement.”
- Not in “epidural or spinal anesthetic procedures.”
- Not for flushing intravascular catheters, for which preservative-free sodium chloride is named.
For the water version and how it compares with sterile water, see the overview and sterile water for injection vs bacteriostatic water.
Questions
What is bacteriostatic saline?
Bacteriostatic 0.9% Sodium Chloride Injection, USP: a sterile, isotonic solution with 9 mg/mL sodium chloride and 0.9% benzyl alcohol as a preservative, in multiple-dose vials.
Is bacteriostatic saline the same as bacteriostatic water?
No. Both contain 0.9% benzyl alcohol, but bacteriostatic saline is 0.9% sodium chloride while bacteriostatic water is plain water for injection.
Can bacteriostatic saline replace bacteriostatic water?
Only if the label of the drug being prepared names it. Both labels refer the choice of vehicle to the drug manufacturer’s instructions.
Is sodium chloride for injection bacteriostatic?
Only when labelled “Bacteriostatic”. Plain 0.9% Sodium Chloride Injection is generally preservative-free, and the bacteriostatic label names it for catheter flushing and for neonates.
What sizes does bacteriostatic saline come in?
Hospira lists 10 mL, 20 mL and 30 mL multiple-dose plastic Fliptop vials.
Sources
- DailyMed: Bacteriostatic 0.9% Sodium Chloride Injection, USP (Hospira): description, contraindications, warnings, how supplied.
- DailyMed: Bacteriostatic Water for Injection, USP (Hospira).
Reviewed against the current DailyMed labels on 11 October 2026.