Bacteriostatic Water for Injection, USP is the one item in this catalogue that is not a compound at all. It is a mixture — water for injection containing a preservative — and that single fact governs everything about how it should be specified and how listings for it go wrong.
| Composition | Water for Injection USP with benzyl alcohol 0.9% w/v (9 mg/mL) |
|---|---|
| Preservative CAS | 100-51-6 (benzyl alcohol) |
| Molecular formula | None — this is a mixture, not a substance |
| Molecular weight | None |
| pH | 5.7 (specification range 4.5 to 7.0) |
| Tonicity | Not isotonic — contains no solute |
| Container | Multiple-dose vial |
| Storage | 20 to 25 °C, USP Controlled Room Temperature |
| Catalogue reference | CA-21 |
It has no molecular weight, and listings that give one are wrong
A molecular formula and a molecular weight are properties of a substance — a single defined chemical species. Bacteriostatic water is a solution of one substance in another. It has a composition, a concentration and a pH; it does not have a formula or a mass.
Listings that assign it a molecular weight — usually 18.02, the mass of water — have made a category error. It is a small thing, but it is a reliable indicator of whether a supplier’s specifications are assembled by someone who understands what they are describing.
Why “bacteriostatic”
The distinction is between bacteriostatic — inhibiting the multiplication of bacteria — and bactericidal, killing them. Benzyl alcohol is added as an antimicrobial preservative that inhibits bacterial growth in the container.
That preservative action is precisely what permits the vial to be a multiple-dose container from which repeated withdrawals may be made. Preservative-free Sterile Water for Injection contains no such agent and is a different product with different handling implications. The two are not interchangeable and should not be treated as the same item under different names.
Preservative systems differ — read the label
Not all USP bacteriostatic water uses benzyl alcohol. Some marketed product instead uses a paraben system — typically methylparaben 0.12% with propylparaben 0.012%. The preservative identity is a property of the specific product, not of the category name, and must be read off the label of the material actually supplied.
Specification
- pH 5.7, within a specification range of 4.5 to 7.0.
- Preservative content — benzyl alcohol at 0.9% w/v, 9 mg/mL.
- Sterility and non-pyrogenicity, per the USP monograph.
- Not isotonic. The solution contains no tonicity-adjusting solute.
- Container closure. Presentations vary; some manufacturers use semi-rigid polyolefin copolymer containers rather than glass.
Regulatory labelling
FDA-approved labelling for benzyl-alcohol-preserved bacteriostatic water carries the statement, in bold on the label:
“NOT FOR USE IN NEONATES.”
The labelling basis given is that benzyl alcohol has been associated with toxicity in that population. This is quoted here as a regulatory labelling requirement, in the words of the approved label, and is reproduced rather than paraphrased for that reason. Paraben-preserved presentations carry a parallel “not for use in newborns” statement.
Handling and storage
Store at 20 to 25 °C (68 to 77 °F), USP Controlled Room Temperature. Unlike every peptide in this catalogue, this product is not refrigerated, and it should not be stored with the cold-chain items.
Discard any container showing particulate matter, cloudiness or discoloration.
Related items in this library
None. This is the only non-compound entry in the catalogue and the only item classified under Reagents & Consumables rather than Research Peptides.
References
Chemical, specification and analytical sources. This list is deliberately limited to chemistry and analytical references.
- Pfizer/Hospira, Bacteriostatic Water for Injection USP — approved product labelling: composition, pH, storage, neonate statement
- DailyMed, Bacteriostatic Water for Injection — label record
- Fresenius Kabi, Bacteriostatic Water for Injection prescribing information — paraben-preserved presentation and parallel labelling
Available from the catalogue
Bacteriostatic Water 10 mL — a 10 mL multiple-dose vial of lyophilised powder in a sealed glass vial, supplied with a lot-matched certificate of analysis. Bulk pricing applies from five vials.
Cosmic Aminos supplies this material as a laboratory reagent for in-vitro research use only. It is not a drug, food, cosmetic or dietary supplement, is not approved by the Food and Drug Administration for any use, and is not for human or veterinary consumption. No dosing, administration or preparation guidance is provided.