Bacteriostatic Water 10mL research monograph — USP injection solvent for research reconstitution
Bacteriostatic Water for Injection (BAC Water) is a USP-defined sterile aqueous diluent containing benzyl alcohol as a bacteriostatic preservative — the standard reconstitution solvent for lyophilized research peptides intended for multi-dose use. Unlike every other compound in this catalogue, BAC Water is a supply item, not a research compound — its purpose is to dissolve and stabilise the peptides researchers are studying. This monograph covers the USP-defined formulation, the role of benzyl alcohol, the specific neonatal contraindication, and what to look for on a quality-grade product.
Composition.
Bacteriostatic Water for Injection, USP is sterile non-pyrogenic water containing 0.9% (9 mg/mL) benzyl alcohol as the preservative (some manufacturers' preparations contain 9 mg/mL or 11 mg/mL). The benzyl alcohol concentration is the defining feature — it is what distinguishes BAC Water from preservative-free Sterile Water for Injection and is the reason BAC Water tolerates multi-dose use over a 28-day in-use window where Sterile Water does not.
Mechanism (preservation rather than pharmacology).
Benzyl alcohol is bacteriostatic — it inhibits growth of gram-positive and gram-negative bacteria and yeasts at the 0.9% concentration used in BAC Water. The mechanism is membrane-perturbation at the preservative-relevant concentration; benzyl alcohol's longer-term clinical safety profile is well-characterised in the registered pharmaceutical record. There is no pharmacological "therapeutic effect" of BAC Water itself — the diluent is biologically inert by intent.
Research applications.
BAC Water's role in peptide research is reconstitution and dilution of lyophilized peptide vials for multi-dose injection contexts. Most peptide research protocols use BAC Water to bring a lyophilized vial up to the working concentration; the benzyl alcohol preservative permits multi-dose access over 14–30 days when the reconstituted solution is refrigerated. Researchers studying peptide stability in solution should be aware that benzyl alcohol can have small effects on peptide conformation in specific cases, though for most peptide research models it is the standard solvent.
Safety considerations specific to BAC Water.
The single largest safety consideration is neonatal contraindication. Benzyl alcohol has been associated with toxicity in neonates (the historical "gasping syndrome"), and the FDA-approved package insert is explicit that for medications used in neonates, only preservative-free Sterile Water for Injection should be used as the diluent, not BAC Water. Researchers working in neonatal models or with research subjects in the neonatal age range should select preservative-free water rather than BAC Water. Additionally, IV administration of BAC Water alone is contraindicated — hypotonic IV without solute can produce hemolysis.
Research context.
BAC Water is the canonical reconstitution solvent for the peptide research market and is supplied at pharmaceutical-grade quality (USP) by major sterile-injectable manufacturers. Researchers should treat it as a defined USP-grade pharmaceutical product, not a research consumable to be sourced informally.
Storage and handling.
Sealed BAC Water vials are stable at controlled room temperature for the labelled shelf life. After the multi-dose vial is first accessed, use within 28 days is the standard recommended in-use limit per the USP-defined preservative-system characterisation. Discard any vial showing visible particulate or discolouration.
Quality and COA considerations.
A meaningful COA / package insert for BAC Water should confirm USP-grade designation, benzyl alcohol concentration (0.9% / 9 mg/mL is the standard), sterility per USP 71, pyrogen / endotoxin per USP 85, and absence of particulate. Major manufacturers' BAC Water carries straightforward FDA-approved labelling; researchers should source from USP-grade sterile-injectable manufacturers rather than research-only suppliers without USP designation.
Research-use note: This monograph is an educational summary of the USP-defined formulation and the appropriate use of Bacteriostatic Water for Injection. The product is FDA-approved as a USP-grade pharmaceutical diluent and carries a specific neonatal contraindication due to benzyl alcohol toxicity in this population. Nothing here is medical advice or a usage recommendation.