Storing a vial
once it is mixed.
Once mixed, a vial goes in the fridge at 2–8 °C and never in the freezer. Mixed with bacteriostatic water it commonly keeps for around four weeks; with plain sterile water, which has no preservative, it is single-use. Label it with the date and the concentration the moment you mix it.
A freeze-dried powder is stable for a long time. A solution is not — the clock starts the moment water goes in, and what the clock says depends on which water you used.
Which water decides how long
Bacteriostatic water is sterile water with about 0.9% benzyl alcohol in it. The alcohol is what suppresses bacterial growth and is the only reason a vial can be entered more than once.
Plain sterile water and saline have no preservative. A vial mixed with either is a single-use vial, whatever the fridge says.
Cold, not frozen
Refrigerate at 2–8 °C. Do not freeze a reconstituted solution: freezing and thawing is its own stress on the molecule, and the powder — which is what freezing is for — is already gone by this point.
Keep it away from light and away from the fridge door, where the temperature swings every time the door opens.
Label it or lose it
Write the date and the concentration on the vial as you mix it, not later. An unlabelled vial three weeks on is a dose you have to reconstruct from memory, and the reconstruction is where the mistakes live.
Storage figures vary by compound, and the numbers here are the general shape of it rather than a rule for any particular one.
How long does a reconstituted peptide last in the fridge?
Mixed with bacteriostatic water, commonly around four weeks at 2–8 °C. Mixed with plain sterile water it is single-use, because there is no preservative in it. The figure varies by compound.
Can you freeze a reconstituted vial?
No. Freezing and thawing a solution stresses the molecule, and freezing is a way of storing the dry powder — which no longer exists once water has gone in. Refrigerate at 2–8 °C instead.
What is bacteriostatic water and why does it matter?
Sterile water with about 0.9% benzyl alcohol added. The alcohol suppresses bacterial growth, which is the only reason a vial can be entered more than once rather than used and discarded.
What should you write on a reconstituted vial?
The date you mixed it and the resulting concentration. Both are easy at the time and impossible to recover later, and the dose you draw depends on the second one.
For informational purposes only — not medical advice