What Is Bacteriostatic Water?

A plain-language explanation of bacteriostatic water, preservatives, label dependence, and limitations.

Bacteriostatic Water for Injection is sterile water that contains an antimicrobial preservative—commonly 0.9% benzyl alcohol in labeled products. “Bacteriostatic” does not mean contamination-proof.

What it is used for

Some drug labels specify bacteriostatic water as a diluent; others specify sterile water, saline, a supplied diluent, or another solution. Never substitute based on a generic article.

Preservative limitations

The preservative helps inhibit some bacterial growth but does not protect against viruses and does not replace aseptic technique. Benzyl-alcohol warnings apply to certain populations and products, including neonatal warnings in FDA labeling.

Check the label

Confirm the exact name, ingredients, container type, expiration date, storage instructions, and whether the medication label permits that diluent.

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