Chapter 4
Peptide Preparation & Handling
4.1 Dosing Fundamentals
How to Calculate Your Dose
- Define Your Target (in mcg)
- Compute Concentration: (Vial mg × 1000) ÷ Solvent mL
- Find mcg per Syringe Unit: Concentration ÷ 100 units/mL
- Calculate Units to Draw: Desired mcg ÷ mcg/unit
- Round & Record
Worked Example (10 mg vial)
- • Target Dose: 300 mcg
- • Solvent: 1.0 mL → Concentration = 10,000 mcg/mL
- • mcg per Unit: 100 mcg/unit
- • Units to Draw: 300 ÷ 100 = 3 units
4.2 Reconstitution Step-by-Step
"Most people screw this up — and never even realize it."
Reconstitution means dissolving a lyophilized (freeze-dried) peptide in a sterile solvent to obtain a measurable solution. It is the single most decisive step for accuracy and stability: getting it right prevents waste, dosing errors and degradation of the compound.
Which Solvent to Use?
- Bacteriostatic water — the research standard. It contains about 0.9% benzyl alcohol, a mild preservative that limits bacterial growth and lets you use the same vial for several weeks.
- Sterile saline (0.9% NaCl) — a possible alternative, but with no preservative the solution keeps for a much shorter time. Reserve it for immediate use.
What You'll Need
- • 1 vial of lyophilized peptide
- • 1 vial of bacteriostatic water
- • 1 sterile graduated insulin syringe (U-100, 29–31 G)
- • Alcohol swabs
- • A clean, disinfected surface
The Procedure, Step by Step
Room Temperature & Disinfection
Remove the lyophilized vial from cold storage and let it return to room temperature (~10–15 min). Swab the rubber stoppers of both vials with an alcohol wipe, then let them dry.
Slow-Draw the Solvent
With an insulin syringe (29–31 G), slowly draw up the chosen volume of bacteriostatic water (see the concentration table below).
Inject Down the Wall
Hold the vial tilted (~45°) and inject the water slowly down the glass wall — never directly onto the powder, to avoid mechanically degrading the peptide.
Dissolve — Never Shake
Gently roll the vial between your palms until fully dissolved. Never shake: violent agitation can denature the peptide structure.
Inspect Clarity
The solution must be perfectly clear, free of particulates or cloudiness. If in any doubt, do not use it.
Label & Store
Write the reconstitution date and concentration on the vial, then store it in the refrigerator (2–8°C). See §4.3 for shelf-life.
How Much Water to Add?
The volume of water you add sets the final concentration of your solution. The rule is universal, valid for any lyophilized peptide:
Total amount (mg) ÷ Volume added (mL) = Concentration (mg/mL)
Here are the concentrations obtained for a 10 mg vial:
| Water added | Concentration | Quick reference |
|---|---|---|
| 1 mL | 10 mg/mL | 0.1 mL = 1 mg |
| 2 mL (recommended) | 5 mg/mL | 0.2 mL = 1 mg |
| 5 mL | 2 mg/mL | 0.5 mL = 1 mg |
The larger the volume added, the lower the final concentration — which makes micro-doses easier to measure precisely.
Worked Example (10 mg vial + 2 mL)
Verified calculation
- • 10 mg ÷ 2 mL = 5 mg/mL (i.e. 5,000 mcg/mL)
- • On a U-100 insulin syringe: 100 units = 1 mL
- • 0.1 mL = 10 units = 0.5 mg
- • 0.2 mL = 20 units = 1 mg
- • 0.3 mL = 30 units = 1.5 mg
To convert a target dose (in mcg) into syringe units, follow the detailed method in §4.1.
Mistakes to avoid at all costs:
- Shaking the vial vigorously (risk of denaturation) — simply roll it gently
- Injecting water straight onto the powder instead of down the glass wall
- Using non-sterile water or forgetting to disinfect the stoppers
- Getting the concentration calculation wrong
- Freezing the solution after reconstitution
- Working in a non-disinfected environment
4.3 Storage Best Practices
- Lyophilized (powder) peptides: Store at -20°C or colder; stable for 2+ years
- Reconstituted peptides: Refrigerate at 2-8°C; use within 4-8 weeks
- Avoid: Repeated freeze-thaw cycles, direct sunlight, heat exposure
- Always: Use sterile technique, fresh needles, and clean work surfaces
4.4 FAQ — Reconstitution
What is the best dilution for a 10 mg vial?
A common choice is 2 mL of bacteriostatic water, giving a concentration of 5 mg/mL. It offers the best balance between easy math and accurate draws.
Can I use sterile saline instead of bacteriostatic water?
Yes, but saline contains no preservative, so the solution keeps for a much shorter time. Bacteriostatic water is preferable for use over several weeks.
Should I shake the vial to dissolve the powder?
No, never. Gently roll the vial between your palms until fully dissolved. Vigorous shaking can denature the peptide structure.
Can a peptide be frozen after reconstitution?
No. Freezing after reconstitution can damage the peptide structure. Keep the solution refrigerated, between 2 and 8°C.
How long does a reconstituted solution last?
Typically 4 to 8 weeks in the refrigerator when prepared with bacteriostatic water. If the solution turns cloudy or changes appearance, do not use it.