How to store peptides

Storage at a glance

The rest of this guide explains each row, where approved medicines follow different rules, and why FDA is stricter about GLP-1 drugs that arrive warm.

Freeze-dried powder

Temperature

Peptide makers agree on cold for the long term. Bachem's guidance is to keep the powder sealed tight below -15 °C, and colder still, -50 °C or lower, for long-term storage.¹ GenScript's figure is -20 °C, out of bright light, where it expects most freeze-dried peptides to last several years, depending on the sequence.² For short-term use, Bachem considers a refrigerator at 4 °C acceptable.¹

Sequence matters. Bachem lists peptides that contain asparagine (Asn), glutamine (Gln), methionine (Met), cysteine (Cys) or tryptophan (Trp) as having limited shelf lives.¹¹⁰

Approved freeze-dried medicines show that no single rule fits every product. The labels split two ways: tesamorelin (EGRIFTA SV and WR) and a Fresenius Kabi hCG product are stored at room temperature, 20 to 25 °C, while ZOMACTON somatropin is refrigerated at 2 to 8 °C.³⁶⁵⁴ Each of those is a limit set for one product, so for any other vial, the storage condition printed on its label is the guide.

Moisture

Peptides tend to be hygroscopic, meaning they take up water from the air. Bachem's advice is to open a cold container only after it has warmed to room temperature inside a desiccator, because moisture the powder absorbs dilutes its peptide content and may make it less stable.¹¹⁰ GenScript singles out peptides containing aspartic acid (Asp), glutamic acid (Glu), lysine (Lys), arginine (Arg) or histidine (His) as prone to absorbing moisture, and keeps them in a tightly capped vial inside a desiccator.²

Both makers advise removing only what is needed, quickly, and closing the container tight again,¹¹⁰² and GenScript returns the rest to a freezer, preferably below -20 °C, under dry conditions.²

Light and air

Peptides containing Cys, Met or Trp oxidize easily. GenScript advises limiting their exposure to air and keeping vials tightly capped,² and Bachem mentions oxygen-free water or reducing agents as options when dissolving them.¹¹⁰ Light is the other factor: the EGRIFTA SV, EGRIFTA WR and ZOMACTON labels all keep their vials in the original carton, shielded from light.³⁶⁵

Peptides in solution

How long a mixed vial keeps

Dissolving a peptide starts a clock. Bachem's position is that peptides should not be stored dissolved, even in sterile, oxygen-free solution, because they may slowly degrade chemically.¹ GenScript calls the shelf life of peptides in solution very limited, worst of all for sequences with Cys, Met, Trp, Asp, Gln or an N-terminal Glu, and adds that bacteria can also degrade a peptide in solution.² The diluent labels agree: a solution is mixed well, used promptly and kept only where the dissolved drug's maker says so.⁸¹¹

Approved products that are mixed before use show how far apart those directions can be:

The tesamorelin labels say their two formulations differ in reconstitution instructions and storage requirements and are not substitutable,⁶ so one product's rules do not carry over to another. The sources behind this guide hold no tested limit for any research peptide after mixing, which is why the safest reading of the makers' advice is to dissolve only what the work needs and record the mixing date on the vial.

Freezing, thawing and aliquots

If a solution must be kept, GenScript recommends a buffer at pH 5 to 6, single-use aliquots held at -20 °C, and no freeze-thaw cycles, with a 0.2 micron filter as a way to strip out possible bacterial contamination.² Bachem likewise keeps aliquots frozen below -15 °C and does not recommend long-term storage of solutions, especially for peptides containing Asn, Gln, Cys, Met or Trp.¹¹⁰ Aliquots cut both the number of freeze-thaw cycles and the number of times the stock meets air, and GenScript also advises against opening the stock vial repeatedly.²

Approved products take the opposite line for their own mixed solutions: EGRIFTA SV, EGRIFTA WR, ZOMACTON and the Fresenius Kabi hCG vial all say not to freeze after mixing.³⁶⁵⁴ Where a product has a label, its instruction comes first.

Splitting a solution requires its concentration on record. The reconstitution calculator works the concentration out from the amount and the volume, and the peptide calculator converts a set amount into a volume, so each aliquot can be labeled with what it holds. The reconstitution guide covers the mixing itself.

Opened diluent vials

The bacteriostatic water label stores the vial at 20 to 25 °C and gives no instruction to refrigerate it after opening.⁸ Once a multiple-dose vial has been opened, meaning its stopper has been pierced, CDC says to write the date on it and throw it out within 28 days, unless its manufacturer gives a different date, and never to use it after the original expiration date.⁹ The EGRIFTA WR instructions apply the same 28-day limit to their bacteriostatic water.⁶

Single-dose vials, such as sterile water for injection, are not kept at all: CDC rules out pooling or saving whatever is left in a single-dose vial.⁹ Bacteriostatic water and the other handling supplies are listed on the supplies page.

Shipping and arrival

Bachem typically sends its freeze-dried peptides out at ambient temperature, with the recommended long-term storage condition noted on the label.¹ One approved freeze-dried peptide gives a sense of scale: the EGRIFTA SV label sets 20 to 25 °C and tolerates excursions between 15 and 30 °C, a limit tested for that product alone.³

FDA is stricter about GLP-1 drugs. It says the package inserts of injectable GLP-1 drugs call for refrigeration, reports complaints of compounded GLP-1 drugs arriving warm, and advises patients against using an injectable GLP-1 drug that has arrived warm or without enough refrigeration, since that can affect its quality.⁷

Shipping details for orders are on the shipping page. On arrival, move each vial to the storage condition printed on its label, and keep it in its box away from light until it is needed.