From this articleRetatrutideMetabolism & gewicht · €44.95 – €219.95
From this articleGHK-CuHuid, haar & cosmetisch · €31.95 – €49.95Anyone who orders peptides in powder form needs a solvent. Almost every guide then says "bacteriostatic water" or simply "BAC water", and sometimes "sterile water". The difference lies in a single ingredient, but that one ingredient determines how long a reconstituted vial remains usable. In this article you will read what bacteriostatic water is exactly, how it differs from sterile water for injection, how long it keeps and where you can and cannot buy it.
Buy bacteriostatic water? Every vial of peptide from PeptideCenter comes with 3 ml of BAC water free of charge; separate 10 ml vials are available.
What is bacteriostatic water (BAC water)?
Bacteriostatic water is sterile, purified water to which 0.9% benzyl alcohol has been added (9 mg per ml). Benzyl alcohol is a preservative that inhibits the growth of bacteria — hence "bacterio-static": it does not kill bacteria, but keeps them in check. This means a vial of BAC water can be punctured several times without the contents spoiling. The water itself meets the same requirements as water for injections: free of particles, pyrogens and micro-organisms.
BAC water comes in glass vials with a rubber stopper, usually 3 ml, 10 ml or 30 ml. The American 30 ml vial from Hospira (Pfizer) is the best known; in Europe 3 ml and 10 ml are more common because the shelf life after opening is limited and a smaller vial means less waste.
What is sterile water (water for injections)?
Sterile water for injection — in the pharmacy "water for injections" or aqua ad iniectabilia — is the same purified, sterile water, but without preservative. It comes in single-use ampoules: once an ampoule is open, the contents are no longer protected against bacterial growth and whatever is left must be discarded. For laboratory work where you measure out a volume once and do not keep the rest, that is no problem. For a vial of peptide that you use in portions over several weeks, it is.
The difference in one table
| Bacteriostatic water (BAC water) | Sterile water for injection | |
|---|---|---|
| Conserveermiddel | 0,9% benzylalcohol | Geen |
| Packaging | Vial with rubber stopper (3, 10 or 30 ml) | Single-use ampoule (5 or 10 ml) |
| Meerdere keren aanprikken | And | No |
| Houdbaarheid na openen | Up to 28 days, refrigerated | Direct gebruiken, rest weggooien |
| Suitable for peptides in powder form | Ja, standaardkeuze | Only when the whole vial is used at once |
| Available from | Research suppliers | Pharmacy (on request), medical wholesalers |
Why peptides are reconstituted with BAC water
Peptides such as retatrutide or GHK-Cu are supplied freeze-dried: a white or lightly coloured powder at the bottom of the vial. That powder is stable, but only usable after reconstitution — adding a measured amount of solvent. Because a reconstituted vial is in practice not used up in one go, a solvent with a preservative is the logical choice. Without benzyl alcohol, every puncture of the stopper would be a chance of contamination, and the solution would become unreliable within a few days.
The amount of water you add determines the concentration of the solution; how to calculate it and which mistakes to avoid is explained in the reconstitution and storage guide. The rule of thumb for vial size: 3 ml is enough for one vial of peptide, 10 ml for several vials or for anyone who wants to dilute more generously.
How long does BAC water keep?
Unopened, bacteriostatic water keeps until the date on the label, stored at room temperature (15–25 °C) and away from direct light. After the first puncture, the standard rule for vials with preservative applies: a maximum of 28 days, refrigerated. After that, discard the rest, even if the vial still looks clear — benzyl alcohol inhibits bacterial growth, but not indefinitely. Write the opening date on the vial; that avoids guesswork.
A reconstituted peptide vial follows the same logic: store refrigerated at 2–8 °C and use within about 30 days. Cloudiness, particles or discolouration are always a reason to stop using the solution.
Where to buy bacteriostatic water — and where not
Pharmacy: supplies ampoules of sterile water for injection, sometimes only on request. Bacteriostatic water with benzyl alcohol is generally not stocked by pharmacies.
Drugstores: sell demineralised or distilled water for irons and batteries. That is not sterile and contains no preservative — unsuitable for reconstituting peptides, however clear it looks.
Making it yourself: the search "make BAC water at home" is common, and the answer is no. Sterility and the exact benzyl alcohol concentration cannot be guaranteed at home, and one contaminated vial makes the entire peptide vial worthless.
Research suppliers: the normal route. At PeptideCenter every vial of peptide comes with 3 ml of BAC water free of charge; add a separate 10 ml vial if you reconstitute several peptides at once. Shipped from our own stock; ordered before 17:00 means shipped today.
Frequently Asked Questions
What is BAC water?
BAC water is short for bacteriostatic water: sterile water with 0.9% benzyl alcohol as a preservative, supplied in a vial that can be punctured several times. It is the standard solvent for freeze-dried peptides.
How long does BAC water keep after opening?
A maximum of 28 days, refrigerated. Unopened until the expiry date on the label, at room temperature and away from light.
What is the difference between sterile water and bacteriostatic water?
Sterile water for injection contains no preservative and is single-use; bacteriostatic water contains 0.9% benzyl alcohol and can be used for up to 28 days after opening. Otherwise the water itself is equivalent.
What is water for injections?
The pharmacy name for sterile water that complies with the European Pharmacopoeia (aqua ad iniectabilia): free of particles, pyrogens and micro-organisms, packed in single-use ampoules.
Can I buy BAC water at the pharmacy or drugstore?
No. The pharmacy supplies sterile water for injection in ampoules; drugstores sell demineralised water, which is not sterile. Bacteriostatic water is bought from research suppliers.
Heb ik 3 ml of 10 ml nodig?
For one vial of peptide, 3 ml is more than enough; at PeptideCenter it is included with every order as standard. If you are reconstituting several vials, or want to dilute more generously, choose a separate 10 ml vial.
Bronnen
- Europese Farmacopee, monografie Water for injections (0169).
- United States Pharmacopeia, General Chapter <797>: shelf life of multi-dose vials after first puncture (28 days).
- Hospira/Pfizer, product information Bacteriostatic Water for Injection, USP (0.9% benzyl alcohol).
- PeptideCenter, Dissolving Peptides: The Complete Reconstitution and Storage Guide.
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