Definition
Sterile water containing 0.9% benzyl alcohol, which inhibits bacterial growth in vials that are accessed repeatedly.
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol as a preservative. Benzyl alcohol inhibits the growth of most bacteria, so a vial reconstituted with bacteriostatic water can be accessed through its septum several times over a period of days with reduced risk of microbial contamination. It does not sterilise a contaminated solution. In laboratory work, the main consideration is compatibility: benzyl alcohol can be cytotoxic in some cell culture systems and may interact with certain peptides. Plain sterile water is preferred for single-use preparations and preservative-sensitive assays. The choice of diluent should be recorded on the vial label.