Bacteriostatic water

What is bacteriostatic water for?

Bacteriostatic water is labeled for use only as a sterile solvent or diluent vehicle for other drugs given by intramuscular, intravenous or subcutaneous injection [1]. It is not itself a medication; peptides and other drugs supplied as a dry powder are typically mixed with it using a vial and syringe before injection. It carries a benzyl alcohol preservative because it is supplied as a multiple-dose vial [1].

Why does the label warn against certain uses?

The label carries three specific warnings [1]. It is "NOT FOR USE IN NEONATES," because benzyl alcohol has been associated with toxicity in newborns; a preservative-free diluent should be used for them instead [1]. It also warns that intravenous administration of bacteriostatic water without a drug dissolved in it may cause hemolysis, the breakdown of red blood cells [1]. The label directs storage at 20 to 25°C [1].

Does bacteriostatic water affect sterility testing?

FDA's guide for inspecting lyophilized drug manufacturing notes that a product may be labeled for reconstitution with bacteriostatic water, but recommends that sterile water for injection (WFI) be used instead when testing that product, so contamination in the drug itself is not masked by the water's antimicrobial preservative [2]. That is a manufacturing quality-control point, not a change to how a pharmacy dispenses the finished product for patient use.