Reconstitution

Reconstitution is the procedure of dissolving a lyophilized (freeze-dried) peptide in a sterile diluent before use in research. Correct reconstitution preserves peptide activity, maintains sterility for the in-solution shelf-life, and ensures accurate dosing math at the bench.

Overview

Most research peptides arrive as a white powder cake at the bottom of a sealed glass vial. They must be dissolved in a sterile, mildly preservative-containing liquid · most commonly Bacteriostatic_water (sterile water with 0.9% benzyl alcohol) · before they can be drawn into a syringe.

Required materials

• Lyophilized peptide vial (sealed, do not open the stopper)
• Bacteriostatic water (10 mL multi-use vial recommended)
• Sterile insulin syringes (29 or 31 gauge, 0.5 mL or 1 mL)
• 70% isopropyl alcohol swabs
• Sharps disposal container

The math

Reconstitution math is volume-per-unit: how many units on the syringe deliver the target microgram or milligram dose.

Formula:

desired_dose_µg / (vial_size_µg / diluent_mL) = mL needed

Worked example. You have a 5 mg (5000 µg) vial. You add 2 mL of bacteriostatic water. You want a 250 µg dose:

250 / (5000 / 2) = 250 / 2500 = 0.1 mL = 10 units on a U-100 insulin syringe

A U-100 syringe has 100 units per mL, so 0.1 mL = 10 units. See Reconstitution_calculator for a live tool.

Procedure

1. Wipe both vial stoppers with alcohol swabs and let dry.
2. Draw your chosen diluent volume into a sterile syringe (typically 1, 2, 3, or 5 mL depending on the dose-per-unit math you want).
3. Insert the needle into the peptide vial at a 45° angle. Aim the stream at the glass wall, not at the powder cake.
4. Inject slowly, letting the diluent dissolve the cake on its own. Do not shake. Swirl gently if undissolved material remains after 5 minutes.
5. Label the vial with reconstitution date, diluent volume, and resulting concentration.
6. Store reconstituted vial at 2–8 °C. Use within the peptide-specific shelf (see individual articles).

What NOT to do

• Don't shake. Mechanical agitation denatures peptide tertiary structure. Swirl, don't shake.
• Don't use tap water, distilled water, or saline. Bacteriostatic water only.
• Don't reconstitute and freeze. Lyophilized cake handles freeze cycles; dissolved peptide does not.
• Don't reuse a draw needle. One needle per draw. Replace before each injection.

Per-peptide reconstituted shelf-life

See also

• Bacteriostatic_water
• Storage
• Sterile_technique
• Reconstitution_calculator · interactive tool

References

• USP General Chapter <797> · [Pharmaceutical Compounding · Sterile Preparations](https://www.usp.org/compounding/general-chapter-797). The authoritative reference for sterile manipulation, single-needle-per-draw technique, and beyond-use-date assignment.
• USP General Chapter <1191> · Stability Considerations in Dispensing Practice.
• Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. "Stability of protein pharmaceuticals: an update." Pharm Res. 2010;27(4):544-75. PMID 20143256.