Bacteriostatic Water

Bacteriostatic water is sterile water that contains a small amount of benzyl alcohol (typically 0.9%) as a preservative, which inhibits the growth of bacteria without necessarily killing them (hence “bacteriostatic”).

Key Characteristics

Composition: Sterile water + 0.9% benzyl alcohol

Purpose: The preservative allows the vial to be used multiple times over a period of time (usually up to 28 days after opening) without contamination risk.

Common Uses

• Reconstituting medications — dissolving lyophilized (freeze-dried) drugs like peptides, hormones, or antibiotics into solution for injection
• Diluting medications — bringing concentrated drugs to an appropriate dose
• Compounding pharmacies — used as a diluent in preparing injectable formulations

Bacteriostatic Water vs. Sterile Water for Injection

Important Safety Notes

• Not for newborns or infants — benzyl alcohol can be toxic to neonates
• Not for intrathecal use (spinal injections)
• Should only be used when mixed with a compatible drug — not injected alone in large volumes
• Requires a prescription in many countries and should be used under medical supervision