How to Store Peptides

Short answer

• Dry powder: freezer at about -20 C, away from bright light, in a tightly closed vial.
• Short term dry: a fridge at about 4 C is fine for short periods.
• Mixed: the product's own label sets the time and place. There is no one number for all peptides.
• No label to go on: ask a pharmacist how to store a mixed vial.

Before mixing: storing freeze-dried powder

Temperature

Lab guides agree that dry peptide powder keeps best in the cold. GenScript says to store it at -20 C (GenScript). Bachem says below -15 C, and colder is better, such as -50 C or lower for long storage (Bachem).

For short periods, a fridge at 4 C is fine for some peptides (Bachem). Dry peptides can also handle room temperature for a while, such as during shipping (NIBSC).

Light

Keep the powder away from bright light (GenScript). A closed box in the freezer works well.

Moisture, and warming the vial before you open it

Peptide powder pulls water out of the air. Water in the vial lowers the amount of peptide and can make it break down faster (Bachem).

So lab guides say:

1. Take the closed vial out of the cold.
2. Let it warm up to room temperature before you open it.
3. Work quickly once it is open.
4. Close it tightly again.

A cold vial opened right away can collect water from the air, the same way a cold glass gets wet on the outside. Some peptides take up water more easily. GenScript says those should be kept in a tightly capped vial in a dry box, called a desiccator (GenScript).

After mixing: why liquid keeps less well

Lab guides say peptides should not be stored as a liquid for long. Even a clean, sterile liquid lets them slowly break down (Bachem). GenScript says the same: a liquid has a very short shelf life (GenScript). Drug scientists see the same pattern in protein medicines. A major review sorts the damage into chemical and physical kinds, and covers how makers keep these molecules stable in liquid and in the dry state (Manning and others, 2010).

The product label sets the time limit

The water label says not to store a mixed drug unless the maker of that drug says you can (DailyMed label). So the number of days a mixed vial keeps comes from the product, not from the water. Labels differ from product to product. If there is no label to go on, ask a pharmacist.

What lab handling guides say (research material, not instructions for medicines)

The guides below are written for peptides used in lab research, not for medicines. They are not storage steps for a mixed vial. For that, use the product label or ask a pharmacist.

• Bachem says frozen peptide solutions may keep for a few weeks (Bachem).
• GenScript says each freeze and thaw can break a peptide down a little more, and that lab users split solutions into single use portions (GenScript).
• NIBSC warns that frost-free freezers warm up and cool down, so what is inside goes through small thaws (NIBSC).

Two clocks: the water vial and the mixed vial

There are two separate time limits, and you need to keep track of both.

1. The opened water vial. The CDC says to date an opened multi use vial and throw it out within 28 days, unless the maker gives a different date (CDC).
2. The mixed peptide vial. Its limit comes from the product label, as above.

A simple label on each vial helps. Copy this onto a sticker:

To find day 28, add 28 days to the date you opened it. See how long bacteriostatic water lasts for more on the water vial.

Shipping, travel and fridge outages

Dry peptides can be shipped at room temperature, says Bachem (Bachem). That is because dry powder is much more stable than a liquid. Put it back in the cold once it arrives.

Mixed vials are different. No lab guide gives one safe time out of the fridge for every product. If a mixed vial got warm or your fridge lost power, check the product label. If the label does not say, ask a pharmacist before you use it.

Signs a vial should not be used

The water label gives a clear rule: check that a mixed drug is clear and free of specks or color changes before use (DailyMed label). The label also says not to use the water unless it is clear and the seal is intact.

Watch for:

• cloudiness that was not there before
• specks or bits floating in the liquid
• a change in color
• a broken seal or cap

Before vs after mixing: storage table

To work out the strength of a mix, use the calculator or the mixing chart. For the mixing steps, see how to reconstitute peptides.