What is bacteriostatic water? Shelf life, storage, and Rx status

How long is bacteriostatic water good for after opening?

The short version, and it is a negative: the approved label sets no number for it, so the 28 days in circulation belongs to some other document. Which document, and what that figure governs, is the rest of this section.

The approved label declines to say: three bacteriostatic water labels tracing to NDA 018802 were read in full for this page, the current Hospira record, the Henry Schein repackaged record, and an older US MedSource record whose only NDC is now inactivated. None of the three states a discard interval after first entry. The nearest the Hospira document comes to a clock is aimed at the mixture, not at the water: when diluting or dissolving drugs, mix thoroughly and use promptly.

One label does set a number, and it is not an approved one: a fourth record was pulled for this review, the TM BIOWATER label on DailyMed, and it states refrigerate after opening and discard 30 days after first puncture. DailyMed files that product under the marketing category unapproved drug other and carries the agency's standard notice on it, that the drug has not been found by FDA to be safe and effective and that its labeling has not been approved by FDA. So a discard interval on a bacteriostatic water label does exist. It sits on a document with no FDA finding behind it, it is 30 days rather than the 28 that circulates, and the two numbers come from different kinds of authority.

So where does 28 days come from: USP General Chapter 797, the sterile compounding chapter, whose official questions and answers describe the requirement that multiple-dose containers not be used for more than 28 days unless otherwise specified on the labeling. That is a rule written for compounders, and the same document notes that compounding does not include mixing or reconstituting done in accordance with directions in approved labeling.

The single-dose figure in the same chapter carries a condition the 28 days does not: a conventionally manufactured single-dose container may be used up to 12 hours after initial entry or puncture, but the chapter requires that the container be entered or punctured inside an ISO Class 5 primary engineering control, and opened single-dose ampules must not be stored for any period at all. The 12 hours and the ISO Class 5 clause sit in the same answer in that document. Separating them turns a cleanroom rule into a general one.

It is a separate clock from the beyond-use date: the same document gives the example of a multiple-dose vial with a 60-day beyond-use date that still has to be discarded no later than 28 days after first puncture. Neither figure is the container's expiration date.

And it belongs to the container, not the contents: the 28 days describes how long the preserved diluent container may keep being entered. What happens to a drug dissolved in that water is the solute manufacturer's question, which is exactly where the label's precautions send it, and it is the subject of a separate page on the mixed vial.

Does bacteriostatic water need to be refrigerated?

Not according to the approved label: all three NDA 018802 documents carry the same storage line, store at 20 to 25 degrees C, which is 68 to 77 degrees F, with a pointer to the USP controlled room temperature definition. That is the room, not the fridge, and it is the only temperature any of them names.

The word itself is absent from those three: refrigerate, refrigerated and refrigeration appear zero times across them, before opening or after. A search that returns nothing is still a finding, and on this question it is the finding.

The unapproved label is where the word does appear: the TM BIOWATER record prints store at 20 to 25 degrees C, protect from light, refrigerate after opening, discard 30 days after first puncture, in that order. That record is filed on DailyMed as unapproved drug other and carries the notice that FDA has not found the drug safe and effective and has not approved its labeling, so the line is a manufacturer's instruction rather than a reviewed one. It is the only one of the four labels read here in which the word appears at all.

What the labels do ask for on the vial: not to use it unless the solution is clear and the seal is intact, and to inspect a reconstituted drug for clarity and for freedom from unexpected precipitation or discoloration before administration. Those two lines cover the seal and the solution, and neither mentions temperature.

Where cold storage does belong: to whatever gets dissolved in the water, and only where that product's own manufacturer directs it, which is precisely where the Hospira precautions send the question. A diluent is not the thing being stabilized, which is why a cold-storage window written for a mixed product does not transfer to the water it was mixed with.

What does controlled room temperature mean on the label?

The storage line points at a definition rather than stating one: all three NDA 018802 documents close that sentence with a bracketed pointer, see USP Controlled Room Temperature, which hands the meaning of the number to the compendium instead of spelling it out on the vial. The definition lives in USP General Chapter 659, Packaging and Storage Requirements, under temperature and storage definitions.

What the chapter defines it as: the temperature maintained thermostatically that encompasses the usual and customary working environment of 20 to 25 degrees C, which is 68 to 77 degrees F, with a mean kinetic temperature not to exceed 25 degrees.

It is a band with tolerances, not a single reading: the same definition allows excursions between 15 and 30 degrees C, 59 to 86 degrees F, of the kind experienced in pharmacies, hospitals and warehouses and during shipping. Provided the mean kinetic temperature does not exceed 25 degrees, transient spikes up to 40 degrees C are permitted as long as they do not exceed 24 hours, and spikes above 40 degrees are permitted only if the manufacturer so instructs.

Refrigerator is a separate defined term in the same list: a cold place in which the temperature is controlled between 2 and 8 degrees C, 36 to 46 degrees F. Cold is any temperature not exceeding 8 degrees, cool is 8 to 15 degrees, warm is 30 to 40 degrees, and excessive heat is anything above 40 degrees, so the storage words the two label families use are separately defined conditions rather than points on one sliding scale.

The clause that settles the fridge question at the compendial level: an article for which storage at controlled room temperature is directed may, alternatively, be stored and shipped in a cool place or refrigerated, unless otherwise specified in the individual monograph or on the label. That sentence makes refrigeration permitted rather than required, and it is a different statement from a label directing it, which is the distinction the previous section turns on.

Does bacteriostatic water expire or go bad?

It expires, and that is a federal requirement rather than a house rule: a finished drug product must bear an expiration date determined by appropriate stability testing, and that date is related to the storage conditions stated on the labeling. Bacteriostatic water is a finished drug product, so every vial carries one, printed by whoever made it.

How long an unopened vial lasts is a per-product answer, not a general one: the interval is whatever that manufacturer's stability testing supported, printed on that container, and the regulation ties the date to the storage conditions stated on the labeling. Neither the regulation nor any of the four labels read here supplies a number that would answer how long bacteriostatic water lasts in general, which is why the printed date on the vial in hand is the only one that applies to it.

That date is not the in-use limit: the expiration date belongs to a sealed container held at 20 to 25 degrees C. The 28-day figure belongs to a container that has already been punctured. A vial can sit inside its expiry and past the in-use limit, or the reverse, because the two clocks start on different events.

What going bad looks like, per the label: the only visual rule the document prints is do not use unless the solution is clear and the seal is intact. There is no color scale, no smell test and no cloudiness threshold in the prescribing information, so anything more specific than that sentence is coming from somewhere other than the label.

What the preservative does not cover: benzyl alcohol is named as a bacteriostatic preservative, which is a claim about inhibiting bacterial growth in the water. Nothing in the document extends that claim to the expiry date, to a punctured container's contents, or to whatever was dissolved into it.

What the label says it is, and what it leaves out

The description section is short: sterile, nonpyrogenic, water for injection, plus benzyl alcohol at one of two stated strengths, supplied in a multiple-dose container from which repeated withdrawals may be made to dilute or dissolve drugs for injection.

Bacteriostatic is a claim about growth, not about killing: the label names benzyl alcohol as a bacteriostatic preservative, and nothing in the document describes it as a sterilant or as a rescue for a container that has been contaminated.

The label makes no claim about the solute: there is no statement anywhere in it that the preservative stabilizes, protects or extends whatever gets dissolved into the water. The precautions point the other way, telling the reader not to store reconstituted drug solutions unless the manufacturer of the solute directs otherwise.

What is absent: no in-use interval, no statement about refrigeration of the diluted product, and no maximum volume for the preparation itself, which leaves the volume question to arithmetic on the vial. None of the three NDA 018802 labels states any of them.

How much benzyl alcohol a vial holds

The arithmetic is one multiplication: the stated concentration multiplied by the volume in the container. At 9mg per mL a 30mL vial holds 270mg of benzyl alcohol in total, and at 11mg per mL the 20mL fill in the glass vial holds 220mg.

Per withdrawal it is much smaller: at 9mg per mL, drawing 1mL carries 9mg of benzyl alcohol along with the water, drawing 2mL carries 18mg, and drawing 3mL carries 27mg, which are also the three volumes that set the concentration of whatever the water dissolves.

What the arithmetic does not settle: the benzyl alcohol warning carried on the glycopyrrolate injection label cited below says that although normal therapeutic doses of that product deliver amounts of benzyl alcohol substantially lower than those reported in association with the gasping syndrome, the minimum amount of benzyl alcohol at which toxicity may occur is not known. The multiplication above is exact. The threshold it would be compared against is one that label states is not known.

The newborn contraindication, and where it comes from

What the label says now: due to the potential toxicity of benzyl alcohol in neonates, solutions containing benzyl alcohol must not be used in this patient population, and where water is required for preparing or diluting medications for neonates, only preservative-free sterile water for injection should be used.

What that warning text describes: the gasping syndrome, characterized by central nervous system depression, metabolic acidosis, gasping respirations, and high levels of benzyl alcohol and its metabolites in blood and urine, associated with benzyl alcohol dosages above 99mg per kg per day in neonates and low-birth-weight neonates.

The additional signs it lists: gradual neurological deterioration, seizures, intracranial hemorrhage, blood abnormalities, skin breakdown, liver and kidney failure, hypotension, bradycardia and cardiovascular collapse.

Where the term appears in the indexed literature: a 1982 New England Journal of Medicine report titled The gasping syndrome and benzyl alcohol poisoning, a CDC report that June titled Neonatal deaths associated with use of benzyl alcohol, and an American Academy of Pediatrics statement the following year titled Benzyl alcohol: toxic agent in neonatal units. They are named here for what they are; none of the three is cited as the first record of the syndrome.

The contraindication is absolute rather than dosed: the label bars the population outright, and the warning text states that the minimum toxic amount is not known, so no threshold is printed to calculate against.

Where do you get bacteriostatic water?

Through the prescription channel, in the United States: the Hospira document is filed on DailyMed as a human prescription drug label, its front panel prints Rx only, and its marketing category is a new drug application, NDA 018802. The Drugs@FDA record for that application lists the product, bacteriostatic water for injection in plastic container, with a marketing status of prescription. That is the channel, and it is a pharmacy one.

Which answers the over-the-counter form of the question: an article whose own label prints Rx only, and whose FDA application record reads prescription, is not an over-the-counter article in that record. What follows from that is a regulatory reading of two documents, not a claim about what any particular seller does.

The USP in the name is doing work: the established name on all three labels is bacteriostatic water for injection, USP, and the same documents state the specification behind it: water for injection carrying 0.9% or 1.1% benzyl alcohol, sterile, nonpyrogenic, pH 5.7 with a stated range of 4.5 to 7.0, supplied in a multiple-dose container. Those are the figures a vial has to match to be the article the label describes, and they are the ones worth checking on anything that arrives.

What this page will not do: name a seller. We link a seller's document only where that document is itself the evidence under discussion, as the certificates of analysis on the KLOW page are, and never as a route to buy anything. Naming one here would replace the useful thing, which is the label itself, with a recommendation we are in no position to make.

Do you need a prescription for bacteriostatic water?

The statute answers it, and it answers about the transaction rather than the product: 21 U.S.C. 353(b)(1) reaches a drug that is not safe for use except under the supervision of a licensed practitioner, or that is limited by an approved application to use under such supervision, which is the clause an article marketed under an NDA falls into.

What the paragraph then requires: such a drug shall be dispensed only upon a written prescription of a practitioner licensed by law to administer it, upon an oral prescription of such practitioner which is reduced promptly to writing and filed by the pharmacist, or by refilling either of those where the prescriber authorized the refill. Three routes, and every one of them runs through a prescriber and a pharmacist.

The same paragraph states the consequence of stepping outside them: the act of dispensing a drug contrary to those provisions is deemed to be an act which results in the drug being misbranded while held for sale. The prescription is therefore not paperwork attached to a product that would otherwise be fine, it is the condition that keeps the article from being misbranded at the point it changes hands.

Where the Rx only on the front panel comes from: 21 U.S.C. 353(b)(4)(A) provides that a drug subject to that paragraph is deemed misbranded if at any time prior to dispensing its label fails to bear, at a minimum, the symbol Rx only. The Rx only symbol printed on the Hospira panel is that requirement being satisfied, which is also why the marketing status in the application record reads prescription rather than over the counter.

What the pharmacy channel is, stated plainly: a licensed practitioner writes or calls in the order, a pharmacist fills and files it, and refills happen only where the prescriber said so. That is the whole of the federal answer to where do you get bacteriostatic water, and it describes a process rather than a place.

What it does not settle: whether any particular vial reached anyone through that process is a fact about that transaction, and no reading of the statute can establish it from here. The statute also speaks to dispensing in the United States and says nothing about how any other country classifies the same article.

What does the USP in the name certify?

It names a compendium, and the term is statutory: 21 U.S.C. 321(j) defines official compendium as the official United States Pharmacopoeia, official Homoeopathic Pharmacopoeia of the United States, official National Formulary, or any supplement to any of them. So the three letters at the end of the established name point at a specific book with a specific legal standing, not at a quality adjective.

There is a monograph sitting behind that name: USP-NF carries one titled Bacteriostatic Water for Injection, whose publicly visible definition reads that it is prepared from Water for Injection that is sterilized and suitably packaged, containing one or more suitable antimicrobial agents. The rest of the monograph, including its own packaging and storage statement, sits behind the USP-NF subscription, which is a paywall rather than a missing document.

What claiming the name puts at stake: under 21 U.S.C. 351(b) a drug is deemed adulterated if it purports to be or is represented as a drug the name of which is recognized in an official compendium and its strength differs from, or its quality or purity falls below, the standard set forth in that compendium. Under 21 U.S.C. 352(g) it is deemed misbranded unless it is packaged and labeled as prescribed therein.

It is also why the established name reads the way it does: 21 U.S.C. 352(e)(3) sets the established name as the applicable official name where one has been designated, and otherwise, for an article recognized in an official compendium, the official title in that compendium. That is how the front of the Hospira document arrives at Bacteriostatic Water for Injection, USP instead of a trade name.

And it is a claim a label can simply decline to make: the DailyMed record for the unapproved product covered further up files it as bacteriostatic water injection, without the for Injection, USP compendial title the three NDA 018802 records carry. Two records describing the same kind of article, and only one of them is claiming the monograph.

What the three letters are not: they are not an FDA approval, which is a separate record entirely, and they are not a measurement of the vial in front of anyone. They are a claim of conformance with consequences that attach to whoever made it, which is why the concentration, the pH range and the container type printed above are the checkable part of the label and the letters are not.

What is bacteriostatic water made of?

Two ingredients, and the label names both. Water for injection, which is the sterile nonpyrogenic base, and benzyl alcohol at 9mg per mL or 11mg per mL depending on the presentation, added as a bacteriostatic preservative. There is no buffer, no salt, and no stabilizer for anything dissolved into it, which is where it parts from the saline labels. That composition is why the label still requires the finished preparation to be made approximately isotonic before use, and why it warns that intravenous administration without a solute may result in hemolysis. The preservative changes the container's working life and nothing about the water's tonicity.

Does bacteriostatic water sterilize anything?

No, and the word says so: bacteriostatic describes inhibition of bacterial growth, and the label calls benzyl alcohol a preservative, not a sterilant.

The container starts sterile: the first sentence of the description calls the preparation sterile and nonpyrogenic, so the preservative is protecting a state that already exists.

Technique is still on the label: the precautions direct aseptic technique for single or multiple entry and withdrawal from all containers, and the label sets no exception for the preserved product.

Is it the same as sterile water?

No. The Hospira sterile water label cited below states that the product contains no bacteriostat, no antimicrobial agent and no added buffer, and that it is supplied only in single-dose containers, with the instruction not to reuse the container and to discard the unused portion. Bacteriostatic water carries the preservative and is supplied multiple-dose. The clauses that read the same on both are the indication sentence, the isotonicity requirement and the hemolysis warning. The two documents also differ in smaller ways, including which one states a pH and what the front panel carries, so the ingredient and the container are the difference that matters here rather than the only difference there is. The choice between them is a choice about how many times the container will be entered, and about whether benzyl alcohol is acceptable in the mixture.

Around this page

The neighboring reads: five pages in the library we maintain, each carrying a piece this one only introduces.

• Bacteriostatic water vs sterile water: the two water labels compared row by row, including the in-use clocks.
• Bacteriostatic water vs saline: the salt question, the tonicity numbers, and the restrictions that attach to preserved saline.
• Bacteriostatic water calculator: the water volume needed to reach a chosen concentration in a given vial.
• How water volume changes your units: why the milliliters added rewrite every unit count that follows.
• Storage after reconstitution: the vial once it holds liquid, and what the labels do and do not cover.
• The Decadewise briefing: one label read or one tool like this, in your inbox once a week.

How this page is sourced

Four labels, three of them one product: the Hospira label, a Henry Schein repackaged version and a US MedSource version all trace to NDA 018802 and were each read in full, which is how the absence of an in-use interval was established rather than assumed. No discard interval appears in any of the three, and no occurrence of refrigerate, refrigerated or refrigeration appears in any of them either. The US MedSource record is a 2014 SPL whose only NDC is now inactivated, and it is cited as a historical label rather than a current one. The Hospira sterile water label is cited separately, for the comparison section only.

The fourth label is the counterexample, and it is cited as one: an earlier version of this page said no bacteriostatic water label sets a discard interval. That was wrong. The TM BIOWATER record on DailyMed sets 30 days after first puncture and directs refrigeration after opening, and it was pulled and read in full for this correction on 29 July 2026. It is cited with its marketing category attached, unapproved drug other, because that category is what separates it from the other three and is the reason the page distinguishes an approved label from a label.

The regulatory status comes from two FDA records, not from a summary: the prescription status and the NDA number are structured data elements inside the Hospira label itself, and the application record was read separately in Drugs@FDA. The expiration-date requirement is quoted from the regulation rather than described.

The prescription and compendial answers are quoted from the statute, not paraphrased from a summary: the dispensing routes, the misbranding consequence, the Rx only requirement, the definition of an official compendium, and the adulteration, misbranding and established-name provisions were each read in the United States Code text published by the Government Publishing Office and are cited to the section they sit in. Where this page says what a law provides, that is the law's own wording carried across, and the section numbers are printed so the wording can be checked against it.

The USP material is cited to two USP documents with different standings: the monograph entry is the official USP-NF record, whose public landing page carries the definition sentence quoted here and holds the rest behind the USP-NF subscription, so the packaging and storage statement inside it was not read for this page and nothing is attributed to it. The storage-condition definitions come from the General Chapter 659 revision bulletin USP posts in full, official 1 May 2017, which is why they can be quoted where the monograph cannot.

The gasping syndrome text is quoted from a label that carries it: the version quoted here is the benzyl alcohol warning printed on a current glycopyrrolate injection label, and it is quoted with its own scope intact rather than restated as a general finding.

The 1982 and 1983 records are cited by title: the three publications below are named for what they are, and no case counts or exposure figures from them are reported on this page, because their full texts were not retrievable for this review.

The standard: the full sourcing and citation-verification standard for this site, including who checks a page before it ships, lives on the methodology page.

Last reviewed: 28 July 2026.

1. 1

   Hospira, Inc. Bacteriostatic Water for Injection, USP, prescribing information: description, indications, contraindications, warnings, precautions, how supplied. SPL version 20, effective 22 May 2026. DailyMed, U.S. National Library of Medicine. Current label.

2. 2

   Henry Schein, Inc. (repackager); the repackaged label names Hospira, Inc. as distributor of the source product. Bacteriostatic Water for Injection, USP, 30 mL multiple-dose vial, full prescribing information. DailyMed, U.S. National Library of Medicine. Current label.

3. 3

   BE Pharmaceuticals Inc. Glycopyrrolate Injection, USP, 0.2 mg/mL, prescribing information, benzyl alcohol warning. DailyMed, U.S. National Library of Medicine. Current label.

4. 4

   United States Pharmacopeia. General Chapter <797> Pharmaceutical Compounding, Sterile Preparations: frequently asked questions, updated 11 December 2023, questions 186, 187, 188, 193 and 194. USP document.

5. 5

   Gershanik J, Boecler B, Ensley H, McCloskey S, George W. The gasping syndrome and benzyl alcohol poisoning. N Engl J Med. 1982;307(22):1384-1388. doi:10.1056/NEJM198211253072206. PMID 7133084.

6. 6

   Centers for Disease Control. Neonatal deaths associated with use of benzyl alcohol, United States. MMWR Morb Mortal Wkly Rep. 1982;31(22):290-291. PMID 6810084.

7. 7

   Committee on Fetus and Newborn, Committee on Drugs, American Academy of Pediatrics. Benzyl alcohol: toxic agent in neonatal units. Pediatrics. 1983;72(3):356-358. doi:10.1542/peds.72.3.356. PMID 6889041.

8. 8

   US MedSource, LLC. Bacteriostatic Water for Injection, USP, prescribing information. SPL version 1, updated 7 July 2014; the record's only NDC is now inactivated. DailyMed, U.S. National Library of Medicine. Archived label.

9. 9

   Hospira, Inc. Sterile Water for Injection, USP, prescribing information: description, contraindications, warnings, how supplied. SPL version 10, effective 18 March 2026. DailyMed, U.S. National Library of Medicine. Current label.

10. 10

    U.S. Code of Federal Regulations, Title 21, Part 211, Subpart G, Section 211.137, Expiration dating, paragraphs (a) and (b). U.S. Government Publishing Office. 21 CFR 211.137.

11. 11

    U.S. Food and Drug Administration. Drugs@FDA application record for NDA 018802, Bacteriostatic Water for Injection in Plastic Container, sponsor Hospira, marketing status Prescription. openFDA drug application endpoint. Application record.

12. 12

    TM Biowater, Inc. TM BIOWATER, bacteriostatic water injection, 30 mL multiple-dose vial, NDC 87597-003. Principal display panel and product information. Marketing category unapproved drug other; DailyMed prints the notice that the drug has not been found by FDA to be safe and effective and that the labeling has not been approved by FDA. SPL version 4, effective 18 June 2026. DailyMed, U.S. National Library of Medicine. Current label, set id 4af596eb-7f27-dc59-e063-6294a90aa12b.

13. 13

    United States Code, Title 21, Chapter 9, Subchapter V, Part A, Section 353, Exemptions and consideration for certain drugs, devices, and biological products: subsection (b)(1), dispensing routes and the misbranded-while-held-for-sale provision, and subsection (b)(4)(A), the Rx only symbol requirement. 2023 edition. U.S. Government Publishing Office. 21 U.S.C. 353.

14. 14

    United States Code, Title 21, 2023 edition, three sections read for the compendial questions on this page: Section 321(j), the definition of official compendium; Section 351(b), adulteration where strength differs from or quality or purity falls below the compendial standard; Section 352(g) and 352(e)(3), misbranding where the article is not packaged and labeled as the compendium prescribes, and the established-name hierarchy. U.S. Government Publishing Office. 21 U.S.C. 321; 21 U.S.C. 351; 21 U.S.C. 352.

15. 15

    United States Pharmacopeia. Bacteriostatic Water for Injection, official USP-NF monograph record. The public landing page carries the definition sentence quoted on this page and holds the remainder of the monograph, including its packaging and storage and labeling statements, behind the USP-NF subscription: that is a paywall, not a missing document, and nothing beyond the visible definition is attributed to it here. Record accessed 2 August 2026. doi:10.31003/USPNF_M88830_03_01.

16. 16

    United States Pharmacopeia. General Chapter 659, Packaging and Storage Requirements, Revision Bulletin, official 1 May 2017, incorporated in USP 41-NF 36; temperature and storage definitions section, covering freezer, refrigerator, cold, cool, room temperature, controlled room temperature, warm and excessive heat. Posted in full by USP. USP document.