How long does bacteriostatic water last after opening

The short answer is 28 days from the first puncture, per USP guidelines. After 28 days the vial should be discarded regardless of how much liquid is left.

Storage

Store at controlled room temperature, 20–25 °C (68–77 °F). Do not freeze. Keep the vial away from direct sunlight and heat sources.

Why 28 days

The 0.9% benzyl alcohol preservative inhibits bacterial growth but does not kill bacteria on contact. Over time, with repeated punctures, the risk of contamination rises. The 28-day window is the USP-validated period during which the preservative can reliably keep the solution safe.

Aseptic technique

• Use a new sterile needle and syringe for every withdrawal. Never reuse needles.
• Swab the vial stopper with an alcohol wipe before each withdrawal and let it dry.
• Do not touch the stopper or needle tip with your fingers.

Unopened vials

Unopened vials last until the manufacturer's expiry date printed on the label — typically 2–3 years from manufacturing. Pfizer (Hospira) prints a lot number and expiry date on every label, and you can verify authenticity with Pfizer directly using the lot number.

Signs to discard

If the solution appears cloudy, discolored, or contains visible particles, discard the vial immediately, even if it is within the 28-day window. Visible change means the solution is compromised.