BAC water, short for bacteriostatic water, is sterile water containing 0.9% benzyl alcohol as a preservative to prevent bacterial growth. It’s used in medical settings to dilute or dissolve medications for injection, such as vaccines, insulin, or peptides, allowing multiple doses from a single vial for up to 28 days. It’s suitable for intramuscular, intravenous, or subcutaneous injections but not for neonates due to benzyl alcohol toxicity. Unlike sterile water, which is preservative-free and single-use, BAC water’s preservative makes it safer for multi-dose applications. It has a pH of 4.5–7.0 and is stored at room temperature. Always follow medication instructions for dilution, as some drugs may be incompatible with benzyl alcohol.
