What is bacteriostatic water?
Bacteriostatic water is sterile water containing a bacteriostatic preservative, commonly 0.9% benzyl alcohol. The preservative suppresses bacterial growth after repeated needle entries. It does not make poor sterile technique safe and it does not sterilize a contaminated vial.
BAC water vs sterile water
| Feature | Bacteriostatic water | Sterile water |
|---|---|---|
| Preservative | Usually 0.9% benzyl alcohol | None |
| Typical container use | Designed for multiple withdrawals when the product instructions permit | Commonly intended for single use |
| Main limitation | Not appropriate for every drug, route, patient, or research material | No preservative protection after entry |
Handling principles
- Use a new sterile needle and syringe for every withdrawal.
- Disinfect the stopper and allow it to dry before puncture.
- Do not use cloudy water, particles, damaged seals, or expired material.
- Follow the water manufacturer and target product instructions for storage and discard dates.
- Do not assume every lyophilized compound is compatible with bacteriostatic water.
Why the benzyl alcohol percentage matters
The uploaded eBac certificate identifies benzyl alcohol and reports 0.921%, close to the listed 0.9% specification. The same report lists sterility as passing, endotoxins below 0.25 EU/mL, and pH 6.253.
BAC Water Certificate of Analysis
eBac BAC Water 30 mL, batch EB61901
Benzyl alcohol0.921%
SterilityPass
Endotoxins<0.25 EU/mL
pH6.253
Important: A passing water COA does not establish compatibility, sterility, potency, or safety of any compound mixed with it.