How to reconstitute peptides (and where to buy bacteriostatic water in the UK)

01The short version

Reconstitution is dissolving a freeze-dried peptide in sterile water so it can be measured and used. The steps are simple; the details (water type, technique, concentration) are where people go wrong. This guide covers the method, where to buy bacteriostatic water in the UK, and links to the calculator that does the maths.

02Which water: bacteriostatic vs sterile

Bacteriostatic water is sterile water with 0.9% benzyl alcohol, which stops bacteria growing in a vial that will be punctured several times over weeks. Use it for anything you will draw from more than once. Plain sterile water is for single use. Never tap, bottled or boiled water: not sterile, wrong pH, and it will ruin the peptide.

In the UK, bacteriostatic water is sold by the same suppliers that sell peptides, by medical consumables retailers, and on the larger marketplaces. 10 mL and 30 mL vials are standard; expect £5 to £15. Check the seal is intact and the expiry is in date.

03The method

1. Clean everything. Wash hands, clean a surface, swab the rubber tops of both vials with an alcohol wipe and let them dry.
2. Decide the volume. Use the calculator. More water means a more dilute solution and larger, easier-to-measure doses; 1 to 3 mL is typical for a 5 to 10 mg vial.
3. Draw the water into a sterile syringe.
4. Add it slowly, down the side of the peptide vial, not onto the powder. A hard jet damages the peptide.
5. Do not shake. Swirl gently or leave it to dissolve. Most peptides clear within a few minutes; some take longer.
6. Label the vial with the date and concentration (for example "5 mg / 2 mL = 2.5 mg/mL").
7. Refrigerate. Reconstituted peptides live in the fridge, upright, away from the door. See storage.

04If you are making a nasal spray

The method is the same, then the solution is transferred into a sterile metered nasal pump bottle. The extra variables are the pump volume (usually 0.1 mL per press, but check) and preservation, since a nasal bottle is opened to the air every use. The calculator has a nasal mode. The sterility problem is the reason we do not recommend this for Semax; the comparison with a finished spray explains why.

05Common mistakes

• Shaking the vial.
• Using too little water, so each dose is a few units on the syringe and any error is large.
• Not labelling, then forgetting the concentration.
• Reusing needles.
• Leaving the vial out on the desk.
• Trusting a "dosing chart" from a forum that assumed a different water volume.

COGENT makes two peptide nasal sprays, Semax (FOCUS-01) and Selank (CALM-02), and nothing else. We do not sell the compounds discussed below and this article does not recommend buying them. It exists because people search for these things and deserve an honest answer.