USP MONOGRAPH STANDARD
Bacteriostatic Water for Injection (USP): The Reconstitution Standard
Evidence-based clinical reference guide on 0.9% benzyl alcohol preservative mechanics, bacterial membrane inhibition, multi-dose beyond-use dating (USP <797>), syringe dilution ratios, and pharmaceutical authenticity verification.
🔬 Pharmaceutical Monograph & Physical Parameters
Bacteriostatic Water for Injection, USP
9 mg/mL Benzyl Alcohol (0.9%)
C₇H₈O (Benzyl Alcohol, PubChem CID 734)
4.5 to 7.0 (Target ~5.7)
Slightly acidic to neutral (target 5.7)
Approximately 83 mOsmol/L (Hypotonic)
Hypotonic diluent (83 mOsmol/L)
28 Days Post-Puncture
Multi-dose refrigerated (USP <797>)
2°C to 8°C (Refrigerated)
36°F to 46°F once punctured
STRICTLY DO NOT FREEZE
Ice shear forces fracture peptides
KNOWLEDGE CLUSTER
In-Depth Bacteriostatic Water Research Guides
Explore our specialized peer-reviewed articles analyzing chemical preservative mechanisms, home compounding safety hazards, and third-party laboratory verification.
FORMULATION SCIENCE
Read Scientific Guide →
What Is Bacteriostatic Water?
Pharmacological analysis of 0.9% benzyl alcohol preservative kinetics, bacterial cell membrane disruption, and multi-dose safety versus sterile water.
SAFETY HAZARD ANALYSIS
Examine Clinical Risks →
Can You Make BAC Water at Home?
Why syringe filters fail to remove heat-stable pyrogens/endotoxins, risks of uneven alcohol dissolution, localized necrosis, and sterile abscess hazards.
SOURCING & COAs
View Buyer Checklist →
Where to Buy Bacteriostatic Water
Six-point inspection checklist to identify counterfeit Hospira/Pfizer vials, evaluate glass vs. plastic packaging, and source from licensed distributors.
Frequently Asked Questions: Bacteriostatic Water & Reconstitution
Analytical answers to critical questions regarding storage, freezing contraindications, syringe measurements, and sterility standards.
❓ What is Bacteriostatic Water and how does it work?
Bacteriostatic Water for Injection, USP (BAC water) is sterile, pyrogen-free water containing 0.9% (9 mg/mL) benzyl alcohol as a bacteriostatic preservative. Benzyl alcohol disrupts bacterial cytoplasmic membrane permeability and inhibits microbial replication without denaturing synthetic peptides. This enables safe multi-dose access from the same vial over a 28-day period.
❓ What happens if I use sterile water instead of bacteriostatic water?
Sterile Water for Injection (SWFI) contains zero preservatives. While sterile when sealed, the very first needle puncture introduces ambient airborne microbes and microscopic skin flora. In unpreserved sterile water, bacteria double every 20 to 30 minutes at room temperature, transforming the vial into a bacterial culture within 24 to 48 hours. Injecting contaminated solution creates severe risks of subcutaneous abscesses, cellulitis, and systemic infection.
❓ How long does Bacteriostatic Water last once opened?
Under United States Pharmacopeia (USP <797>) multi-dose compounding standards, Bacteriostatic Water has a maximum Beyond-Use Date (BUD) of 28 days following the initial needle puncture, provided it is continuously refrigerated at 2°C to 8°C (36°F to 46°F) and handled with strict aseptic technique. After 28 days, repeated punctures deplete preservative efficacy, and the vial must be safely discarded.
❓ Can you freeze reconstituted peptides or Bacteriostatic Water?
NO. You must NEVER freeze reconstituted peptides or vials containing Bacteriostatic Water. Freezing causes benzyl alcohol to phase-separate and lose homogeneity, and the formation of sharp ice crystals exerts mechanical shear stress that tears peptide amino acid backbones apart, causing catastrophic loss of potency. Only unmixed, lyophilized (dry powder) vials should be kept in the freezer.
❓ Can I make Bacteriostatic Water at home using distilled water and benzyl alcohol?
Medical literature and pharmacological safety standards strongly warn against DIY reconstitution fluids. Standard home boiling and syringe filters (even 0.22 micron) cannot eliminate bacterial endotoxins (pyrogens), which trigger violent shivering, fever, and immune shocks. Furthermore, benzyl alcohol is oily and difficult to disperse homogenously without pharmaceutical cleanroom homogenizers; uneven concentrations cause localized tissue necrosis or fail to inhibit bacteria.
❓ Why does Bacteriostatic Water sometimes sting upon injection?
A mild, temporary stinging sensation is common and is caused by two factors: the slightly acidic pH of BAC water (USP specification pH 4.5–7.0, typically ~5.7) and the local vasodilatory effect of 0.9% benzyl alcohol. To minimize stinging: allow the drawn dose to warm to room temperature for 5 minutes before administration (cold liquid stings more), inject slowly over 5 to 10 seconds, and ensure the alcohol swab on the skin has completely dried.
❓ How can I spot fake or counterfeit Hospira / Pfizer Bacteriostatic Water?
Authentic Hospira/Pfizer BAC water features distinct security hallmarks: a tamper-evident flip-off plastic cap embossed with 'FLIP OFF', a clear Lot number and expiration date laser-etched onto the label, high-clarity USP Type I borosilicate glass or specialized semi-rigid plastic, and a pH reading between 4.5 and 7.0 on analytical test strips. Fake vials often feature crooked labels, misspelled words, cloudy liquid, or alkaline pH (>7.5) indicating ordinary tap or filtered water.
❓ What is the difference between Bacteriostatic Water and Bacteriostatic Saline?
Bacteriostatic Water contains 0.9% benzyl alcohol in pure sterile water (hypotonic, ~83 mOsmol/L). Bacteriostatic Saline contains 0.9% benzyl alcohol plus 0.9% sodium chloride (isotonic, ~308 mOsmol/L). While bacteriostatic saline reduces injection stinging for some compounds, the sodium and chloride ions can destabilize or 'salt out' sensitive peptide chains (such as Retatrutide, GHK-Cu, or high-molecular-weight incretins). Plain BAC water is the universal standard for peptide reconstitution.
❓ Why is Bacteriostatic Water contraindicated in newborn infants?
Benzyl alcohol is strictly contraindicated in neonates and infants due to 'gasping syndrome.' Neonatal livers lack mature glycine-N-acyltransferase enzyme activity required to conjugate benzyl alcohol into hippuric acid, resulting in toxic accumulation of benzoic acid, severe metabolic acidosis, central nervous system depression, respiratory distress, and cardiovascular collapse. In adults, therapeutic peptide injection volumes yield trace amounts (<4 mg) that are rapidly cleared within 90 minutes.
❓ What syringe should I use to reconstitute and measure peptides?
For reconstitution (mixing), use a 3 mL syringe fitted with a 21G to 25G, 1-inch to 1.5-inch needle to smoothly transfer BAC water without excessive resistance. For research administration (measuring doses), use a U-100 (1.0 mL, 100 units) or U-50 (0.5 mL, 50 units) insulin syringe with a fine 30G or 31G 5/16-inch needle. On a U-100 syringe, each single unit tick mark equals exactly 0.01 mL.