How Long Does Bacteriostatic Water Last?

How long does bacteriostatic water last?

Two clocks run at once on an opened vial: 28 days from the first puncture, and the printed expiration date. Whichever date comes first is the discard date.

How to work out your discard date

Pick your first puncture date in the helper below. It adds the 28 days for you. You can also do the date math by hand.

1. Write down the date you first put a needle through the stopper. This is day 0.
2. Add 28 days. That is your discard-by date.
3. Look at the expiration date on the vial.
4. Your discard date is the earlier of the two.

Example: You first open a vial on March 1. March 1 plus 28 days is March 29. The vial says it expires in December. March 29 comes first, so you throw it out by March 29.

Second example: You first open a vial on May 10. Plus 28 days is June 7. But the printed expiry is May 31. May 31 comes first, so that is the discard date.

A simple timeline

Where the 28-day rule comes from

The 28 days is not printed on the bacteriostatic water label. The label calls it a multiple-dose vial and gives a storage range. It says nothing about how many days it lasts after opening.

The rule comes from three other places:

• CDC: date an opened multiple-dose vial and throw it out within 28 days, unless the maker gives a different date.
• USP chapter 797: an opened multiple-dose container with a preservative gets a 28-day limit, unless the maker says otherwise.
• FDA: in general, use multiple-dose vials of sterile drugs within 28 days after first use. FDA says the risk of contamination goes up after that.

So if someone tells you "the label says 28 days," that is not right, because the label is silent on it. The rule is real, but it is a health guideline.

Unopened vials: the expiration date

An unopened vial is good until the date printed on it. The label shows a lot number and an EXP date on each vial. The CDC says unopened vials are thrown out by the maker's expiration date.

The label says to store the vial at 20 to 25 C (68 to 77 F). That is room temperature. Once the vial passes its printed date, it should not be used, even if it was never opened.

Does it need to be refrigerated?

No, not by the label. The label says to store it at 20 to 25 C (68 to 77 F), and it does not say to refrigerate it, before or after opening.

A fridge does not add days either. The CDC and USP limit is still 28 days. Full details are in does bacteriostatic water need to be refrigerated.

How to store it

• Keep it in the range the label gives: 20 to 25 C (68 to 77 F).
• Write the first puncture date on the vial or a sticker.
• Use clean technique every time you enter the vial. The label asks for this.
• The label does not mention freezing. Its only range is room temperature, and freezing is outside it.

Signs to throw it out

The label says not to use the water unless it is clear and the seal is intact. It also says to look for particles and color change before use. Throw the vial out if:

• The water is cloudy.
• You see bits or particles floating in it.
• The color has changed.
• The seal or stopper is damaged.
• It is past 28 days from first puncture.
• It is past the printed expiration date.

How to date your vial

Mark the vial the day you first open it. Use a small label or a marker on the cap. Write two dates:

• Opened: the date of the first needle.
• Discard by: that date plus 28 days, or the expiry date if sooner.

Writing it down means you do not have to remember. The CDC asks health workers to do the same with every opened multiple-dose vial. In a hospital study, 13% of the vials that did carry an opening date were already past their limit, so check the date each time (Mattner and Gastmeier, 2004).

Bacteriostatic water vs sterile water after opening

Sterile water for injection works in a different way. It has no preservative, and its label says it comes only in single-dose vials: do not reuse the vial, and throw out what is left.

So the 28-day rule is for multiple-dose vials like bacteriostatic water. Sterile water is used once. See bacteriostatic water vs sterile water for a full side-by-side table. For the water itself, see what is bacteriostatic water. Mixed solutions follow their own product label; see how to store peptides.