What is in it
Bacteriostatic Water for Injection, USP is sterile, non-pyrogenic water with 0.9% (9 mg/mL) benzyl alcohol added as a bacteriostatic preservative. It contains no other active ingredient.
Bacteriostatic means it slows the growth of bacteria. It does not mean it kills everything or that the vial can be handled carelessly.
How it differs from sterile water and saline
- Sterile water for injection has no preservative. It is usually meant for a single use and the rest is discarded.
- Bacteriostatic water has the benzyl alcohol preservative, so a vial can be used for more than one draw within the time its label allows.
- Sodium chloride 0.9% (saline) is salt water. Some products say on their own leaflet which diluent to use; follow that, not a general rule.
What the label asks of you
- Write the date you first open the vial on it. A common rule for opened multi-dose vials is to discard them 28 days after first use, unless the label gives a different date.
- Store it as the label says and do not use it if it looks cloudy or contains particles.
- Benzyl alcohol is not used for newborns, and some people are sensitive to it. Your pharmacist can tell you if it suits you.
How the amount of water changes the numbers
The water you add changes the concentration, not the amount of the substance in the vial. More water means each unit on the syringe holds less, so the same dose takes more volume.
The reconstitution calculator turns the vial amount, the water added and your prescribed dose into units on a U-100 syringe.
