The pharmaceutical-grade peptide diluent. Hospira/Pfizer Bacteriostatic Water (NDA 018802) is the FDA-approved standard — sterile water + 0.9% benzyl alcohol that lets you re-puncture a multi-dose vial for ~28 days. Here’s when to use it, when not to, and why neonates have a black-box history with this preservative.
Bacteriostatic Water for Injection (BAC water) is sterile water with 0.9% (9 mg/mL) benzyl alcohol added as an antimicrobial preservative. The USP-NF monograph specifies pH 5.7 (range 4.5–7.0) and the benzyl alcohol concentration. The preservative makes the vial “bacteriostatic” (prevents bacterial growth) but not sterile-after-puncture — you still want clean technique — which is what allows multi-dose use over a window of days to weeks.
For peptide reconstitution this is the dominant default: most peptides are stable in BAC water at the typical reconstitution pH, and the preservative lets you draw multiple doses out of one vial without needing a fresh sterile diluent each time. Compare that to Sterile Water for Injection (SWFI), which has no preservative and is single-use only.
FDA-approved as Hospira/Pfizer Bacteriostatic Water for Injection USP, NDA 018802. USP-NF monograph. Available by prescription, OTC at some pharmacies depending on state, and through compounding pharmacies.
Not all “BAC water” is equal. The Hospira/Pfizer 30 mL multi-dose vial (NDC 0409-3977-03) is the FDA-approved pharmaceutical product manufactured under FDA-inspected GMP — sterilized under validated processes, tested for endotoxins, and labeled with an FDA-cleared in-use shelf life. Hospira was acquired by Pfizer on September 3, 2015; current packaging is “Hospira, Inc., Lake Forest, IL — A Pfizer Company.”
Compounded BAC water from peptide-supply pharmacies (Empower, Hallandale, etc.) is also widely sold and many are reputable, but a compounding pharmacy isn’t held to the same FDA-approved-product standards. Sterility assurance and endotoxin specs vary by pharmacy.
“Research grade” BAC water sold by peptide research-chemical sites is a separate category. Sterility, endotoxin, and preservative-concentration assurance is whatever the seller claims. For injection, this category should be avoided in favor of pharmaceutical or pharmacy-compounded sources.
Benzyl alcohol at 0.9% prevents bacterial replication but doesn’t actively kill organisms already inside the vial. Translation: clean injection technique still matters. The preservative buys you a safe re-entry window of about 28 days.
Per USP <797> and the FDA-approved label, the in-use beyond-use date for a punctured Hospira vial is 28 days at controlled room temperature (20–25 °C). Most peptide reconstitution practice refrigerates after first puncture for additional peptide-stability margin even though the preservative itself doesn’t require it.
Slightly acidic. This is fine for most peptides but is exactly why IGF-1 LR3 aggregates within days in BAC water — LR3 needs a more acidic environment (0.6% acetic acid) to stay soluble.
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Start Tracking FreeBAC water’s prominent “not for use in neonates” warning traces to a real and well-documented incident. In 1982, NICUs at multiple hospitals saw a cluster of newborn deaths from metabolic acidosis, seizures, and gasping respirations. The cause: high cumulative exposure to benzyl alcohol from frequent BAC-water flushes of indwelling catheters and IV lines. Premature infants lack the mature glycine-N-acyltransferase enzyme adults have, so they accumulate benzyl alcohol’s toxic metabolite (benzoic acid) instead of clearing it.
A 1–3 mL BAC-water injection delivers about 0.13–0.39 mg/kg of benzyl alcohol per dose — two to three orders of magnitude below the documented adult tolerated load. The neonate warning is real and important; it is not a meaningful concern for an adult using BAC water for peptide injection. People with documented benzyl alcohol allergy are the relevant adult exclusion.
BAC water’s pH 5.7 is too neutral for LR3. The peptide aggregates within days. Acetic-acid reconstitution gives ~28-day stability. See the IGF-1 LR3 guide.
Per the 1982 incident and AAP statement, BAC water is contraindicated in newborns. Sterile Water for Injection (no preservative) is the substitute, single-use only.
The USP labelling is explicit that preparations containing benzyl alcohol must not be used in epidural or spinal anaesthesia procedures, and must not be used for fluid replacement. Neither is a peptide-reconstitution scenario, but both appear on the same label and are worth knowing if a vial is ever repurposed.
A detail that surprises people: the label warns that intravenous administration of Bacteriostatic Water without a solute may cause hemolysis, and that the solution must be made approximately isotonic before use. Plain water is hypotonic, and red cells in contact with it burst. It is a diluent, not a saline flush and not something to inject by itself.
USP Bacteriostatic Water is supplied at either 0.9% (9 mg/mL) or 1.1% (11 mg/mL) benzyl alcohol depending on the product. The difference is small but it is real, and it matters if you are reconstituting several vials and tracking total preservative exposure, or if you are unusually sensitive. Read the vial rather than assuming.
Rare but real. Skin reactions to multi-dose vaccines or local anesthetics that contain benzyl alcohol are the typical history. If documented, use Sterile Water for Injection plus single-use vial discipline.
Vendor literature splits. Most peptide-supply pharmacies recommend BAC water for PEG-MGF reconstitution; some communities use 0.6% acetic acid by analogy with IGF-1 LR3. There is no published peer-reviewed PK comparison to settle this. The dominant practice is BAC water; if your supplier specifies otherwise, follow their instruction.
Pre-filled with a typical Bacteriostatic Water for Injection setup. Edit any field — the draw updates live.
Insulin syringe — 100 units = 1 mL
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Controlled room temperature (20–25 °C / 68–77 °F). Excursions allowed to 15–30 °C. Don’t freeze. Keep out of direct sunlight.
28-day BUD at controlled room temperature per USP <797> and the Hospira label. Many peptide users refrigerate the punctured vial as a defensive habit — the preservative itself doesn’t require it, but cold storage gives margin against any borderline-contaminated draw.
Most BAC water vials outlive the peptide they’re reconstituting. A typical compounded peptide vial is reconstituted to last ~28 days; the BAC water 30 mL vial typically lasts months across many peptides. Date each vial when you first puncture it.
| Diluent | When to Use | In-use BUD |
|---|---|---|
| Bacteriostatic Water (this guide) | Default for most peptides. Multi-dose use OK. | 28 days |
| Sterile Water for Injection (SWFI) | Single-dose use, neonate-safe, benzyl alcohol allergy | Single use |
| 0.6% Acetic Acid | IGF-1 LR3, IGF-1 DES, peptides that aggregate at neutral pH | ~28 days |
| 0.9% Sterile Sodium Chloride (saline) | When isotonic vehicle is preferred or for nasal spray formulations | Single use unless preserved |
| Distilled, tap, spring or “purified” water | Never. Distilled water is not sterile and carries no preservative — distillation removes minerals, not spores. | — |
The rule against non-sterile diluents usually gets stated as a generic caution, so here is a concrete case. A search of the FDA’s FAERS adverse-event database turns up a single report naming the peptide humanin: a 56-year-old, September 2024, coded serious, with the diluent recorded as distilled water. The reported reactions were dizziness, weakness, blurred vision, facial paresis, paralysis, respiratory failure and botulism.
FAERS reports are self-submitted and establish no causality, and that cluster is the classic descending flaccid paralysis of a contaminated injection rather than anything in the peptide’s pharmacology. That is precisely the point. The peptide was almost certainly not the problem — the water was. Distillation removes dissolved solids; it does not sterilise, and Clostridium spores survive it comfortably.
Bacteriostatic water is inexpensive and the preservative is the entire reason it exists. This is the one supply in the process where substituting something that looks equivalent has a documented worst case. See the humanin guide for the full report.
Bacteriostatic Water for Injection is sold for research use only. If you are sourcing it for research, we recommend Lyvn — every batch third-party tested with the full laboratory panel published on the product page.
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For research use only. Not for human consumption. 21+.
Build your protocol, log every dose, monitor your body's response, and get reminders so you never miss a dose.
Start Tracking FreeBacteriostatic Water for Injection (BAC water) is sterile water with 0.9% (9 mg/mL) benzyl alcohol added as an antimicrobial preservative. The USP-NF monograph specifies pH 5.7 (range 4.5 to 7.0) and the benzyl alcohol concentration. The preservative prevents bacterial growth in the vial so you can re-puncture and draw multiple doses over a window of days to weeks, rather than needing a fresh sterile diluent each time. It is the dominant default for peptide reconstitution.
Benzyl alcohol at 0.9% is bacteriostatic, not bactericidal: it prevents bacterial replication but does not actively kill organisms already inside the vial. Translation: clean injection technique still matters. The preservative buys you a safe re-entry window of about 28 days at controlled room temperature per USP <797> and the FDA-approved Hospira label.
Bacteriostatic water is the default for most peptides and supports multi-dose use with a 28-day in-use BUD. Sterile Water for Injection (SWFI) has no preservative and is single-use only, but it is the neonate-safe option and the substitute for anyone with benzyl alcohol allergy. 0.6% acetic acid is used for peptides that aggregate at neutral pH (IGF-1 LR3, IGF-1 DES) and gives roughly 28-day stability. 0.9% sterile sodium chloride (saline) is used when an isotonic vehicle is preferred or for nasal spray formulations and is single-use unless preserved.
The FDA-approved label and USP <797> give a 28-day beyond-use date at controlled room temperature (20 to 25 C) after first puncture. Most peptide users refrigerate the punctured vial as a defensive habit even though the preservative itself does not require it — cold storage gives margin against any borderline-contaminated draw. Pre-puncture, store sealed vials at controlled room temperature; do not freeze and keep out of direct sunlight. Date each vial when you first puncture it.
Bac water carries a prominent 'not for use in neonates' warning that traces to a real 1982 NICU incident: cumulative benzyl alcohol exposure from frequent BAC-water flushes caused a cluster of newborn deaths from metabolic acidosis, seizures, and gasping respirations (Gershanik et al., NEJM 1982, PMID 7133084; CDC MMWR 1982). Premature infants lack the mature glycine-N-acyltransferase enzyme adults have and accumulate the toxic metabolite benzoic acid. For adults at peptide-reconstitution doses (1 to 3 mL), benzyl alcohol exposure is two to three orders of magnitude below the documented adult tolerated load. The neonate warning is real and important; it is not a meaningful concern for an adult using BAC water for peptide injection. Documented benzyl alcohol allergy is the relevant adult exclusion.
Avoid bac water for IGF-1 LR3 and IGF-1 DES because the pH 5.7 is too neutral and the peptide aggregates within days; use 0.6% acetic acid instead. Avoid in neonates and infants under 2 (1982 gasping-syndrome precedent), in anyone with documented benzyl alcohol allergy, and for intrathecal or intraventricular use (benzyl alcohol is neurotoxic in CSF). PEG-MGF is contested: most peptide-supply pharmacies recommend bac water but some communities use 0.6% acetic acid by analogy with LR3; there is no published peer-reviewed PK comparison.
Hospira/Pfizer Bacteriostatic Water USP (30 mL multi-dose vial, NDC 0409-3977-03, NDA 018802) is the FDA-approved pharmaceutical gold standard, manufactured under FDA-inspected GMP with validated sterilization, USP <85> endotoxin testing, and audited preservative concentration. Compounded BAC water from peptide-supply compounding pharmacies (Empower, Hallandale) is also widely sold and many are reputable, but the standards vary by pharmacy. 'Research grade' BAC water from peptide research-chemical sites is a separate category with whatever sterility and preservative assurance the seller claims; this category should be avoided for injection in favor of pharmaceutical or pharmacy-compounded sources.
Disclaimer: This guide is for educational and informational purposes only and is not intended as medical advice, diagnosis, or treatment. The compounds discussed are not FDA approved for human use. Always consult a qualified healthcare provider before starting any new supplement or peptide protocol. StackTrax does not sell peptides or supplements directly — purchase links go to third-party vendors. StackTrax is not responsible for the products, quality, or business practices of any third-party vendor.
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StackTrax guides cover peptides and compounds that are not FDA-approved for the uses discussed. The dosing, reconstitution, and safety information is compiled from published research and community protocols for educational purposes only.
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