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Reconstitution, step by step

How to mix a peptide vial

All peptides ship as a dry powder. Before use, you dissolve the powder in bacteriostatic water. That step is called reconstitution.

The WikiPep mascot, holding a vial and pointing

Four steps, about five minutes. Step three is the one people get wrong, because it needs to go slowly. If you are not sure how much water to add, the calculator works it out for you.

You’ll need:Peptide vialBAC water1 mL U-100 syringeAlcohol pads
Wiping a vial stopper with an alcohol pad
STEP 1

Wipe both rubber tops

Pop off the plastic caps. Wipe the rubber stopper on the peptide vial and on the water vial with a fresh alcohol pad. Let them air dry for a few seconds.

Drawing water from an upside-down vial
STEP 2

Draw the water

Not sure how much? The calculator picks an amount that keeps your doses on round marks.

There is no single right volume for a vial size. It depends on the dose you are taking: the water sets the concentration, and the concentration decides how many units you draw. Each compound page shows the volume that makes its doses land on a readable mark, and the calculator works it out for any combination.

Water running down the inside of the vial wall
STEP 3

Add it slowly down the glass

Push the needle through the stopper at an angle and let the water run down the inside wall. Spraying straight onto the powder can cause foaming.

Gently rolling a vial
STEP 4

Swirl, don’t shake

Roll the vial between your fingers until the liquid is clear. Label it with the date and store it in the fridge.

Bacteriostatic water or sterile water?

Bacteriostatic water is sterile water with 0.9% benzyl alcohol added. The alcohol stops bacteria from growing, which is why one vial can be drawn from many times. Its label calls it a multiple-dose product. Plain sterile water has no preservative and is meant for a single use, so once it has been opened it isn’t kept.

The bacteriostatic water label carries a boxed warning that it is not for use in newborns, because benzyl alcohol has been linked to toxicity in neonates.

Storing a mixed vial

Mixed peptides are kept in the fridge, at 2–8 °C (36–46 °F), away from light. Each compound page repeats this under its FAQs. Unopened bacteriostatic water is a room-temperature product (20–25 °C on its label).

How long a mixed vial lasts

There are two separate questions here.

  • Sterility. Once a multiple-dose vial has been punctured, standard healthcare practice is to discard it within 28 days unless its manufacturer gives a different date, and straight away if sterility is in doubt. That is why step 4 says to write the date on the label.
  • Whether the peptide is still intact. For most unapproved peptides this has not been measured in published studies, so there is no reliable number to give. The 28 days is about contamination, not about the peptide.

If the liquid is cloudy

A properly mixed peptide is clear. Cloudiness, floating particles or a change of color are signs that something is wrong. Injectable labels, including the bacteriostatic water label itself, say not to use a solution that is not clear.

If too much water went in

Nothing is lost. The same amount of peptide is in the vial; it is just more dilute, so each dose takes more units on the syringe. The calculator takes the vial size and the actual amount of water and works out the new number of units. The one practical limit is a 1 mL syringe: past 100 units a dose no longer fits in one draw.

mg, mcg and units

1 mg is 1,000 mcg. “Units” on an insulin syringe are a volume, not an amount of drug: on a U-100 syringe, 100 units is 1 mL, so 10 units is 0.1 mL. How much peptide those 10 units hold depends entirely on how much water went into the vial. IU (international units) are something else again, a measure of biological activity, and can’t be converted to mg without the product’s own figure.

Sources

  1. Pfizer (Hospira): Bacteriostatic Water for Injection, prescribing information
  2. The Joint Commission: Managing multi-dose vials of injectable medication