How to Mix (Reconstitute) a Peptide Vial

What bacteriostatic water is

Bacteriostatic water is sterile water with a small amount of benzyl alcohol added. The benzyl alcohol stops bacteria from growing, so one vial can be used for more than one dose. Its label says it is only for mixing or diluting medicines. (Details here come from Hospira’s label, which covers vials with 0.9% or 1.1% benzyl alcohol.)

The label says not to use it for newborns, because benzyl alcohol can harm them. It also says to use a mixed medicine promptly and not to store it unless the medicine’s maker says you can. Which mixing liquid to use comes from your product’s instructions and your healthcare provider.

How long a punctured vial lasts: pharmacy standards (USP <797>) set a 28-day limit for a multi-dose vial after a needle first goes in, unless the maker says otherwise. The FDA also advises throwing away a compounded GLP-1 multi-dose vial 28 days after first use, even if its label says it lasts longer. That is the longest you should keep it. It doesn’t mean every mixed medicine stays good for 28 days.

Working out the strength: mg divided by mL

Once the vial is mixed, its strength is the total amount of drug divided by the total amount of liquid. A 5 mg vial mixed with 2 mL of liquid is 5 ÷ 2 = 2.5 mg/mL. A 10 mg vial mixed with 1 mL is 10 ÷ 1 = 10 mg/mL. Those are strengths, not dose suggestions. Work out the strength for each water amount.

To turn a prescribed dose into an amount on a U-100 syringe, use this: amount in mL = prescribed mg ÷ strength in mg/mL. Then units = mL × 100 (U-100 means 100 units fill 1 mL, so 1 unit is 0.01 mL). In the first example, 0.25 mg ÷ 2.5 mg/mL = 0.10 mL = 10 units. In the second, 0.25 mg ÷ 10 mg/mL = 0.025 mL = 2.5 units. The second amount is small enough that the lines printed on your syringe, and how small an amount it can measure, really matter.

Write the strength you worked out on the vial or its label, along with the date and the exact storage directions. Don’t borrow a storage time from a different vial. The mixing liquid’s label and the drug’s label may say different things. Follow whichever directions are more specific to your product, and ask a pharmacist if they aren’t clear.

Example: drawing from a Zepbound vial

The instructions for the Zepbound single-dose vial walk through drawing a dose step by step. They use a syringe and needle bought separately, for example a 1 mL syringe and needle your healthcare professional recommends. Pull 0.5 mL of air into the syringe, push that air into the vial, and turn the vial upside down with the needle still in. Pull the plunger past the 0.5 mL line, tap the syringe so the bubbles rise, then push the plunger tip back up to the 0.5 mL line. They say to throw away an opened vial after use, even if there’s medicine left in it.

The Zepbound multi-dose vial uses the same basic steps (air in, turn it upside down, clear the bubbles, set the plunger), but the dose line is 0.6 mL. On a U-100 syringe, those amounts are 50 and 60 units. The label itself gives them in mL. Use a new sterile syringe and needle for every injection. This example shows how to read a label. It isn’t a suggestion to use any particular dose or product.