Peptide storage and beyond-use dates

Start with the first table and read it across, not down. A reconstituted vial is not one container, it is three — the sealed powder before you touch it, the solution once water is in it, and the bottle of water itself — and each has its own instruction. On EGRIFTA WR those numbers are 7 days for the mixed drug and 28 for the water bottle, printed two sentences apart on the same label. Quoting the wrong one of those overstates the drug's clock fourfold.

The second table is the point of the page. Sorted by the clock, the 6 approved labels give 7, 14, 21, 28, 30 and 60 days — a spread of 8.6× for products that are all lyophilised powders, all reconstituted with a benzyl-alcohol-preserved diluent, all injected subcutaneously. Now read the temperature column: SEROSTIM, NOVAREL, PREGNYL and OMNITROPE all require the fridge, GONAL-f allows either, and EGRIFTA WR forbids it outright — "Do not freeze or refrigerate EGRIFTA WR after it has been mixed with the Bacteriostatic Water for Injection." Products cannot differ in the direction of an instruction unless the instruction belongs to the product.

That is why the third table matters. "28 days" is quoted at peptide buyers as though it were one fact and it is at least four unrelated ones, none of them a stability figure for an unapproved compound. It is CDC's infection-control rule about a punctured multi-dose vial; it is EGRIFTA WR's clock on the water bottle; it is GONAL-f's stability figure for follitropin alfa; and it is OMNITROPE's figure for a pen cartridge, on a label that gives the reconstituted 5.8 mg single-patient-use vial 21 days instead. Four provenances, one number, and whoever quoted it to you probably could not say which they meant.

The last table is what this sheet will not tell you, printed where you would look for it rather than buried in a disclaimer. For a peptide with no marketing authorisation there is no beyond-use date, because establishing one means stability testing a specific formulation in a specific container and no manufacturer has published any. The rows above are not a menu to pick from — they disagree by 8.6× and they contradict each other on refrigeration, so there is no consensus to borrow even if borrowing were sound. Anyone who quotes you 28 or 60 days for BPC-157 is quoting it off a different drug.

Three containers, three clocks — what each label says at each stage

One row per approved product. Read across: the sealed powder, then the solution once it is mixed, then the bottle of diluent. Each cell is the temperature the label states, with the days underneath.

The bottom row is the configuration most readers are actually in, and two of its three cells are empty on purpose. The inclusion rule for the rows above it is narrow so the comparison stays like-for-like: an FDA-approved lyophilised powder whose own label directs reconstitution with a benzyl-alcohol-preserved diluent. SEROSTIM appears at 4 mg only — the 5 mg and 6 mg vials take unpreserved Sterile Water for Injection and are single-dose, a different container with a different problem. PREGNYL is included with its solvent named precisely rather than rounded off: it is not Bacteriostatic Water for Injection, USP but "water for injection with sodium chloride 0.56% and benzyl alcohol (preservative) 0.9%" — the same preservative at the same strength in a saline vehicle. OMNITROPE's diluent is a third preservative strength again, 1.5% benzyl alcohol, where the standalone product is sold at 0.9% or 1.1%.

The clock after mixing: 6 approved labels, 6 different answers

Sorted shortest first. The last column is the one to read twice — these products do not merely allow different lengths of time, they disagree about whether the fridge is right at all.

Every figure here is from the product's own FDA-approved labelling and none is interpolated. The spread is 8.6×, which is the arithmetic reason a figure cannot be borrowed between rows: if 60 days were a property of benzyl-alcohol-preserved water, EGRIFTA WR would not discard at 7. The refrigeration column is the stronger argument. Four of these labels require 2–8 °C after mixing, GONAL-f permits either, and EGRIFTA WR prohibits it — a reader who has internalised "reconstituted peptides go in the fridge" as a general rule is already wrong about an approved product, and could not have known which one without reading its label. Nothing in this table is a dose, a frequency or a schedule.

Where “28 days” actually comes from — four clocks, and a label that states none

The figure every peptide storage sheet prints, traced to each of the unrelated places it genuinely appears. Not one of them is a stability date for an unapproved peptide.

The bottom row is the one worth keeping. All seven standalone Bacteriostatic Water for Injection, USP labels on DailyMed — Hospira, Fujian Genohope, ProPharma, Henry Schein, HF Acquisition/HealthFirst, Medical Purchasing Solutions and US MedSource — were retrieved as XML and searched on 20 September 2026 against the 18 September publication. The strings “discard”, “punctur”, “beyond”, “in-use”, “28 day”, “expir” and “shelf” occur zero times in all seven. The water does not answer the question; it hands it over — “Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute.” For an unapproved peptide there is no manufacturer of the solute in that sense, so the sentence terminates with nobody on the other end of it. What remains is CDC's 28 days for the punctured bottle, which is about keeping bacteria out of the water and says nothing about whether the peptide dissolved in it is still intact, and it is capped: “The beyond-use-date should never exceed the manufacturer’s original expiration date.”

What this sheet will not tell you about an unlabelled vial

The refusals, printed where the answer would go. Five of the six rows have no figure, and the sixth belongs to CDC rather than to any product.

This table is the page. Everything above it is evidence for it. A beyond-use date is not a fact about peptides in general and it is not a fact about bacteriostatic water — it is the output of a stability study run on one formulation in one container, and no such study has been published for any unapproved peptide. The practical consequence is not that you should assume a long date or a short one, but that you have no date, which is a different and more uncomfortable position than the internet's confident 28. What you do have is CDC's rule for the punctured water bottle, the printed expiry on the products you bought, and a clinician who can see what you are actually holding. No beyond-use date exists. Every figure in the rows above belongs to a different molecule, and the six of them disagree by a factor of more than eight, so none of them can be borrowed.

Frequently asked questions

How long does a reconstituted peptide last in the fridge?

For an unapproved peptide, nobody has published an answer and this page will not invent one. What can be sourced is how far apart the answers are for products that HAVE been tested: 7, 14, 21, 28, 30 and 60 days across 6 FDA-approved lyophilised products, all mixed with a benzyl-alcohol-preserved diluent. That is a 8.6× spread, and the labels also disagree about the fridge itself — EGRIFTA WR says "Do not freeze or refrigerate EGRIFTA WR after it has been mixed with the Bacteriostatic Water for Injection", while SEROSTIM, NOVAREL, PREGNYL and OMNITROPE all require 2–8 °C. A number that swings by a factor of 8.6 between molecules is not a property of the class, so there is nothing to carry across.

Is 28 days the beyond-use date for a peptide vial?

No, and the figure has at least four different origins, none of them a peptide. It is CDC citing USP General Chapter <797> — "Once a multi-dose vial is opened (e.g., needle-punctured) the vial should be dated and discarded within 28 days unless the manufacturer states another date for that opened vial" — which is about bacteria entering a punctured stopper, not about the drug degrading. It is EGRIFTA WR's instruction to throw away the BACTERIOSTATIC WATER BOTTLE after 28 days, on a label that gives the mixed drug 7. It is GONAL-f's genuine 28-day stability figure for follitropin alfa. And it is OMNITROPE's 28 days for a pen cartridge, on a label that gives the reconstituted 5.8 mg vial 21. Four clocks, one number.

Does bacteriostatic water tell you how long the mixed vial keeps?

No. All seven standalone Bacteriostatic Water for Injection, USP labels on DailyMed were retrieved as XML and searched on 20 September 2026; the strings "discard", "punctur", "beyond", "in-use", "28 day", "expir" and "shelf" occur zero times in every one. The label explicitly defers instead: "Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute." It points at the drug. For a research peptide there is no manufacturer of the solute in that sense, and the sentence runs out.

Should a reconstituted vial go in the fridge or at room temperature?

That depends entirely on the compound, and the approved labels prove it by contradicting each other. EGRIFTA WR: "Store reconstituted EGRIFTA WR at room temperature at 20°C to 25°C (68°F to 77°F)" and, in the patient leaflet, "Do not freeze or refrigerate EGRIFTA WR after it has been mixed". SEROSTIM 4 mg: refrigerated at 2°C to 8°C for up to 14 days. NOVAREL: "the solution should be refrigerated and used within 30 days". PREGNYL: refrigerated, discard after 60 days. GONAL-f allows either. One instruction cannot be right for all of them, so there is no default to apply to a vial whose label does not say.

How long does the bottle of bacteriostatic water last once punctured?

This is the one question on the page with a usable figure, and it is CDC's rather than the bottle's: date the vial at first puncture and discard within 28 days "unless the manufacturer states another date for that opened vial", never past the printed expiry — "The beyond-use-date should never exceed the manufacturer’s original expiration date." EGRIFTA WR, which supplies a 30 mL bottle of it with the drug, tells patients the same thing in its own words: "Throw away (discard) any Bacteriostatic Water for Injection left in the bottle 28 days after first use." Note what that does not say: the drug mixed from that water gets 7 days, not 28.

Can I freeze a reconstituted peptide to make it last longer?

There is no published basis for doing that with an unapproved compound, and the approved labels point the other way: EGRIFTA WR, SEROSTIM, PREGNYL and OMNITROPE all say "Do not freeze" in as many words, at one stage or another. None of those prohibitions is about your compound, and the absence of a prohibition is not a permission — it is an absence of testing. Freezing and thawing a protein is a stability question that has to be answered experimentally for each formulation, and for research peptides nobody has published the experiment.

How should the sealed powder be stored before I mix it?

Even this has no general answer. Among the approved comparators, OMNITROPE requires the unmixed vials refrigerated at 2° to 8°C in the original carton, GONAL-f permits either the fridge or 20–25 °C, and EGRIFTA WR, NOVAREL and PREGNYL all specify room temperature — EGRIFTA WR at "20°C to 25°C (68°F to 77°F) in the original box to protect from light; excursions permitted to 15°C to 30°C". Three of the six also direct light protection and three do not mention it. If the products that have been tested cannot agree, a figure for one that has not been tested would be a guess in the shape of a fact.

What about a compounded peptide from a pharmacy — does it have a beyond-use date?

Yes, and it is the compounding pharmacy's, printed on their vial. A compounded preparation is not FDA-approved and has no FDA-reviewed label, so its beyond-use date is assigned per batch by the pharmacy that made it under the standards it compounds to. Read that label; nothing on this page replaces it, and nothing on this page can be used to extend it.

Why does this page not just give me a safe number to use?

Because a printed sheet outlives the caveats around it. The 6 sourced clocks here run from 7 days to 60 — 8.6× apart — and disagree on refrigeration, so any single figure would be a choice we made rather than a fact we found, and it would be taped to a cupboard door long after the reasoning was lost. The honest position is that for an unapproved peptide the beyond-use date is unknown, and the useful thing this sheet can do instead is show you exactly how the known figures behave so you can see why none of them transfers.

Sources

1. [1]Bacteriostatic Water for Injection, USP — FDA prescribing information (Hospira, Inc.), DailyMed, marketing category NDA (NDA 018802). "Bacteriostatic Water for Injection, USP is a sterile, nonpyrogenic preparation of water for injection containing 0.9% (9 mg/mL) or 1.1% (11 mg/mL) of benzyl alcohol added as a bacteriostatic preservative." / "It is supplied in a multiple-dose container from which repeated withdrawals may be made to dilute or dissolve drugs for injection." / "Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute." / "Store at 20 to 25°C (68 to 77°F). [See USP Controlled Room Temperature.]" No post-puncture or beyond-use period appears anywhere in the label.
2. [2]DailyMed SPL search, drug_name=bacteriostatic water — 18 results against the 18 September 2026 publication, of which seven are standalone Bacteriostatic Water for Injection, USP labels (Hospira, Fujian Genohope Biotech, ProPharma Distribution, Henry Schein, HF Acquisition/HealthFirst, Medical Purchasing Solutions, US MedSource). All seven retrieved as XML and searched on 20 September 2026 for "discard", "punctur", "beyond", "in-use", "28 day", "expir" and "shelf". Zero occurrences of any of the seven strings in any of the seven labels.
3. [3]EGRIFTA WR (tesamorelin) for injection — FDA prescribing information (Theratechnologies Inc.), DailyMed, marketing category BLA (BLA 022505; diluent NDA 018802). "Store EGRIFTA WR 11.6 mg vial at room temperature at 20°C to 25°C (68°F to 77°F) in the original box to protect from light; excursions permitted to 15°C to 30°C (59°F to 86°F) [See USP Controlled Room Temperature]." / "Store reconstituted EGRIFTA WR at room temperature at 20°C to 25°C (68°F to 77°F). Discard unused solution of EGRIFTA WR 7 days after mixing. Do not freeze." / "Do not freeze or refrigerate EGRIFTA WR after it has been mixed with the Bacteriostatic Water for Injection." / "Throw away (discard) any Bacteriostatic Water for Injection left in the bottle 28 days after first use."
4. [4]SEROSTIM (somatropin) for injection — FDA prescribing information (EMD Serono, Inc.), DailyMed, marketing category BLA (BLA 020604). The 4 mg presentation is co-packaged with "Bacteriostatic Water for Injection, USP (0.9% benzyl alcohol as preservative) 3.5 mL multiple-dose vials". "Before reconstitution: Store cartons containing SEROSTIM vials and diluent vials at room temperature between 15°C to 30°C (59°F to 86°F)." / "SEROSTIM 4 mg vial reconstituted with Bacteriostatic Water for Injection with 0.9% benzyl alcohol as preservative may be refrigerated at 2°C to 8°C (36°F to 46°F) for up to 14 days." / "Do not freeze reconstituted SEROSTIM vials."
5. [5]OMNITROPE (somatropin) for injection — FDA prescribing information (Sandoz Inc), DailyMed, marketing category BLA (BLA 021426). The 5.8 mg vial is co-packaged with "8 Single-Dose Vials of Bacteriostatic water for injection 1.14 mL", described in Section 11 as "a diluent containing Bacteriostatic Water for Injection with 1.5% benzyl alcohol as a preservative". "Before use, store OMNITROPE vials and cartridges refrigerated at 2° to 8°C (36° to 46°F) in the original carton to protect from light. Do not freeze." / "After reconstitution of the lyophilized powder, the contents of the OMNITROPE vial must be used within 21 days. After the first injection, store the vial in the original carton in a refrigerator at 2° to 8°C (36° to 46°F). Discard unused portions after 21 days." / "After first use, the OMNITROPE cartridge should remain in the pen and kept the original carton in a refrigerator at 2° to 8°C (36° to 46°F) for a maximum of 28 days."
6. [6]GONAL-f (follitropin alfa) for injection — FDA prescribing information (EMD Serono, Inc.), DailyMed, marketing category BLA (BLA 020378). The multi-dose vial is reconstituted with "1 mL Bacteriostatic Water for Injection (0.9% benzyl alcohol), USP". "Store vials refrigerated between 2°C to 8°C (36°F to 46°F) or at room temperature between 20°C to 25°C (68°F to 77°F). Store reconstituted solution refrigerated between 2°C to 8°C (36°F to 46°F) or at room temperature between 20°C to 25°C (68°F to 77°F) and discard unused portion after 28 days. Protect from light" / Patient leaflet: "store it in the refrigerator or at room temperature for a maximum of 28 days from the day the powder was mixed with Bacteriostatic Water."
7. [7]NOVAREL (chorionic gonadotropin) for injection — FDA prescribing information (Ferring Pharmaceuticals Inc.), DailyMed, marketing category BLA (BLA 017016). "When reconstituted with Bacteriostatic Water for Injection preserved with benzyl alcohol 0.9%, the solution should be refrigerated and used within 30 days." / Carton: "Store at room temperature at 20° to 25°C (68° to 77°F), excursions permitted between 15° and 30°C (between 59° and 86°F) [See USP Controlled Room Temperature]. REFRIGERATE RECONSTITUTED PRODUCT AT 2° to 8°C (36° to 46°F) AND USE WITHIN 30 DAYS."
8. [8]PREGNYL (chorionic gonadotropin) for injection — FDA prescribing information (Organon LLC), DailyMed, marketing category BLA (BLA 017692). Its solvent is not bacteriostatic water: "One 10 mL multiple-dose vial of solvent containing: water for injection with sodium chloride 0.56% and benzyl alcohol (preservative) 0.9%". "IMPORTANT: IF NEEDED, THE RECONSTITUTED SOLUTION IS STABLE FOR 60 DAYS WHEN REFRIGERATED. DO NOT FREEZE. USE THE RECONSTITUTED SOLUTION WITHIN 60 DAYS OF RECONSTITUTION." / "Store unopened vial at controlled room temperature 15°C to 25°C (59°F to 77°F). If reconstituted solution in vial is not used immediately, then store refrigerated [2°C to 8°C (36°F to 46°F)] until use and discard after 60 days. Do not shake. Do not freeze."
9. [9]Centers for Disease Control and Prevention, Injection Safety — Clinical Safety Considerations. Citing USP General Chapter 797: "An unopened multi-dose vial should be discarded according to the manufacturer's expiration date. Once a multi-dose vial is opened (e.g., needle-punctured) the vial should be dated and discarded within 28 days unless the manufacturer states another date for that opened vial. The beyond-use-date should never exceed the manufacturer's original expiration date."
10. [10]U.S. Food and Drug Administration — Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (category 2). Cited for the regulator's own position on the compounds this page declines to give a storage figure for. On BPC-157: "FDA has identified no, or only limited, safety-related information for the proposed routes of administration. Therefore, the agency lacks sufficient information to know whether the drug would cause harm when administered to humans."