Editorial note: this article summarises published research on GHRP and GHRH peptides (ipamorelin, sermorelin, CJC-1295, GHRP-2, GHRP-6, hexarelin, tesamorelin). Baclabs does not sell these or any peptide; we supply bacteriostatic water and reconstitution consumables. Nothing here is medical advice.
Knowing how to reconstitute ipamorelin, sermorelin, CJC-1295 or any of the GHRPs comes down to three things: choosing the right reconstitution water, doing the concentration arithmetic correctly, and then handling the solution in a way that does not degrade a fragile peptide before the vial is finished. The arithmetic is the same for every compound in this class; the handling matters more for some than others.
This article gives the full maths for 2 mg and 5 mg vials with tables, explains what the licensed tesamorelin label says about diluent and why it says it, and summarises what the pharmaceutical stability literature actually shows about lyophilised versus reconstituted peptides, freeze–thaw cycles and benzyl alcohol. The pharmacology of the compounds themselves is in the growth hormone secretagogues pillar.
Which reconstitution water: bacteriostatic or sterile?
Lyophilised (freeze-dried) peptides are shipped as a dry powder because peptides in solution degrade far faster than the solid. The diluent choice depends on how the vial will be used.
Sterile water for injection contains nothing but water. It is the correct diluent for a vial that is dissolved and used in a single draw. The tesamorelin (Egrifta) label is the clearest example in this class: each vial is reconstituted with sterile water for injection, the solution must be injected immediately, and anything left is discarded; it must not be refrigerated or frozen [1][2]. That instruction is a single-use product design, not a statement that preserved water harms the peptide.
Bacteriostatic water is sterile water with 0.9 per cent benzyl alcohol added as an antimicrobial preservative. It is the appropriate diluent for a multi-dose vial that will be punctured repeatedly over days or weeks, because each puncture is a chance to introduce organisms. Bacteriostatic water is accepted for multi-dose use for up to 28 days after first puncture. A 2 mg or 5 mg research vial drawn from daily is exactly this situation. The comparison is set out in full in bacteriostatic water vs sterile water.
How to reconstitute ipamorelin and other GH peptides: the formula
Every calculation uses one relationship:
Concentration (mcg/mL) = peptide mass in the vial (mcg) ÷ volume of diluent added (mL)
Convert milligrams to micrograms first: 1 mg = 1,000 mcg, so a 2 mg vial holds 2,000 mcg and a 5 mg vial holds 5,000 mcg. Then relate the concentration to the syringe. A U-100 insulin syringe is graduated in “units” where 100 units = 1 mL, so:
1 unit = 0.01 mL, and mcg per unit = concentration (mcg/mL) ÷ 100
To find the volume that contains a given amount of peptide: volume (mL) = amount (mcg) ÷ concentration (mcg/mL), and units = volume × 100.
Worked example: ipamorelin, 2 mg vial
Add 2 mL of bacteriostatic water to a 2 mg vial. Concentration = 2,000 mcg ÷ 2 mL = 1,000 mcg/mL. Each unit on a U-100 syringe holds 1,000 ÷ 100 = 10 mcg. A 100 mcg quantity is therefore 0.1 mL, or 10 units; 200 mcg is 20 units. The vial contains 20 draws of 100 mcg.
| 2 mg vial: diluent added | Concentration | mcg per unit | Units for 100 mcg | Units for 200 mcg | Units for 300 mcg |
|---|---|---|---|---|---|
| 0.5 mL | 4,000 mcg/mL | 40 | 2.5 | 5 | 7.5 |
| 1 mL | 2,000 mcg/mL | 20 | 5 | 10 | 15 |
| 2 mL | 1,000 mcg/mL | 10 | 10 | 20 | 30 |
| 3 mL | 667 mcg/mL | 6.67 | 15 | 30 | 45 |
Worked example: sermorelin reconstitution with bac water (5 mg vial)
Add 2.5 mL of bacteriostatic water to a 5 mg vial. Concentration = 5,000 mcg ÷ 2.5 mL = 2,000 mcg/mL, so each unit holds 20 mcg. A 200 mcg quantity is 0.1 mL, or 10 units. With 2 mL instead, the concentration is 2,500 mcg/mL, 25 mcg per unit, and 200 mcg is 8 units. Neither is more correct; the higher dilution simply gives larger, easier-to-read syringe volumes.
| 5 mg vial: diluent added | Concentration | mcg per unit | Units for 100 mcg | Units for 200 mcg | Units for 500 mcg |
|---|---|---|---|---|---|
| 1 mL | 5,000 mcg/mL | 50 | 2 | 4 | 10 |
| 2 mL | 2,500 mcg/mL | 25 | 4 | 8 | 20 |
| 2.5 mL | 2,000 mcg/mL | 20 | 5 | 10 | 25 |
| 3 mL | 1,667 mcg/mL | 16.67 | 6 | 12 | 30 |
| 5 mL | 1,000 mcg/mL | 10 | 10 | 20 | 50 |
Two practical constraints shape the choice of volume. Very small volumes (0.5 mL into a 2 mg vial) make every unit worth 40 mcg, so a one-unit error is a 40 mcg error. Very large volumes may not fit a 2 mL or 3 mL vial once the powder’s own volume is accounted for. Research vials are typically small glass vials of a few millilitres; 1 to 2.5 mL of diluent is the usual compromise. Whatever the volume, the amounts cited in the literature for these compounds are small: the CJC-1295 trials used 30–90 mcg/kg weekly or fortnightly [3], the hexarelin study used 1.5 mcg/kg twice daily [4], and the sermorelin paediatric trials used 30 mcg/kg daily [5].
Technique: keeping a fragile peptide intact
Peptides are damaged by shear, heat, light and repeated phase changes. The tesamorelin label’s mixing instruction is a good general model: add the diluent, roll the vial gently for 30 seconds, do not shake, and check that the solution is clear, colourless and free of particles before use [2]. Directing the diluent down the inside wall of the vial rather than onto the powder reduces foaming. Cloudiness or visible particles after full dissolution mean the peptide has aggregated or the vial was contaminated; that solution should not be used.
Use a fresh sterile needle and syringe for every draw, swab the stopper before each puncture, and record the date of first puncture on the vial. From that date the 28-day multi-dose window for bacteriostatic water runs, regardless of how much remains; see bacteriostatic water storage and shelf life.
Stability: lyophilised versus reconstituted
The lyophilised powder is the stable form. Drying a peptide removes the water that drives hydrolysis and deamidation, which is why manufacturers freeze-dry protein medicines in the first place; the pharmaceutical stability literature treats residual moisture, light and heat as the main threats to a dried solid [6]. A sealed vial kept frozen or, for shorter periods, refrigerated, protected from light, is far more stable than any solution.
Once reconstituted, degradation accelerates. Manning and colleagues’ review of protein pharmaceutical stability lists the main chemical routes in solution as deamidation of asparagine and glutamine, oxidation of methionine (and other susceptible residues such as cysteine and tryptophan), aspartate isomerisation and hydrolysis, alongside physical aggregation, and stresses that the chemical and physical pathways feed each other [6]. Hexarelin and GHRP-6 both contain tryptophan, and sermorelin (GHRH 1-29) contains both methionine and asparagine. Laboratory practice for stock solutions is to keep them cold and split them into single-use aliquots so the stock is not repeatedly warmed and cooled. For a multi-dose vial the practical version of this advice is: refrigerate at 2–8 °C after reconstitution, do not freeze the reconstituted vial, keep it out of light, and finish it within the 28-day window.
Benzyl alcohol and peptides: what the literature says
Benzyl alcohol is the most widely used preservative in multi-dose protein formulations, and it is not inert. Pharmaceutical studies on recombinant proteins show that it can accelerate aggregation by binding to the protein and favouring partial unfolding: this has been demonstrated for interleukin-1 receptor antagonist [7], interferon alfa-2a [8] and granulocyte colony-stimulating factor, where 0.9 per cent benzyl alcohol accelerated aggregation at pH 7 and the effect was much greater at 37 °C than at 25 °C [9]. A review of antimicrobial preservatives concluded that partial rather than global unfolding is the mechanism [10].
Three caveats keep this in proportion. First, those studies concern large, folded therapeutic proteins of 150 to 300 amino acids, whose tertiary structure can be perturbed; the GHRPs are five to six residues and the GHRH analogues 29 to 44, with little tertiary structure to unfold. Second, the effect was strongly temperature-dependent, which is another argument for refrigeration. Third, the preservative is there because an unpreserved multi-dose vial carries a microbial risk that is better documented than the aggregation risk. Bacteriostatic water is the accepted diluent for multi-dose peptide vials; the label instruction for sterile water on single-use products like tesamorelin reflects their single-use design, not a finding that benzyl alcohol damages GHRH analogues.
Diluent supply
Multi-dose vials need a preserved diluent. Baclabs supplies UK-stocked bacteriostatic water in 30 mL vials, enough for a dozen or more 2 mL reconstitutions from one bottle; see the reconstitution guide for the general method, and the CJC-1295 and ipamorelin article or the tesamorelin vs sermorelin article for the pharmacology of the compounds being reconstituted.
Frequently asked questions
How much bacteriostatic water do I add to 5 mg of ipamorelin?
Any volume that fits the vial works; the concentration changes, not the peptide. Adding 2 mL gives 2,500 mcg/mL (25 mcg per unit on a U-100 syringe); adding 2.5 mL gives 2,000 mcg/mL (20 mcg per unit); adding 5 mL gives 1,000 mcg/mL (10 mcg per unit). Choose the volume that gives easily read syringe graduations.
Can sermorelin be reconstituted with bacteriostatic water?
Yes. A multi-dose sermorelin vial drawn from over days needs a preserved diluent, and bacteriostatic water’s 0.9 per cent benzyl alcohol supports use for up to 28 days after first puncture. A 5 mg vial with 2.5 mL gives 2,000 mcg/mL, or 20 mcg per unit. Sterile water suits only a vial used in a single draw.
Why does the tesamorelin label say sterile water only?
Because Egrifta is a single-use product: each vial is reconstituted and injected immediately, with any remainder discarded and no refrigeration of the mixed solution [1][2]. A preservative has no role in a vial used once. That instruction does not transfer to research vials that are punctured repeatedly, where an unpreserved solution carries a microbial risk.
How long does reconstituted ipamorelin or CJC-1295 last in the fridge?
The multi-dose limit set by the bacteriostatic water is 28 days from first puncture. The peptide itself degrades in solution over that time, faster if warmed or exposed to light [6]; refrigerate at 2–8 °C, keep it dark, and do not freeze a reconstituted multi-dose vial.
Does benzyl alcohol damage peptides?
In studies of large recombinant proteins, 0.9 per cent benzyl alcohol accelerated aggregation, most strongly at 37 °C [7][9]. Small peptides such as the GHRPs have little tertiary structure to unfold, and the effect is much smaller when refrigerated. For a multi-dose vial, the preservative’s protection against contamination is the better-documented benefit.
References
- EGRIFTA (tesamorelin for injection) prescribing information. US FDA, 2010
- EGRIFTA SV (tesamorelin for injection) prescribing information. US FDA, 2019
- Prolonged stimulation of growth hormone and IGF-I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. Teichman et al., Journal of Clinical Endocrinology & Metabolism, 2006
- Growth hormone status during long-term hexarelin therapy. Rahim et al., Journal of Clinical Endocrinology & Metabolism, 1998
- Once daily subcutaneous GHRH therapy accelerates growth in GH-deficient children during the first year of therapy. Geref International Study Group. Journal of Clinical Endocrinology & Metabolism, 1996
- Stability of Protein Pharmaceuticals: An Update. Manning MC et al. Pharmaceutical Research, 2010
- Mechanism for benzyl alcohol-induced aggregation of recombinant human interleukin-1 receptor antagonist in aqueous solution. PubMed, 2005
- Role of benzyl alcohol in the unfolding and aggregation of interferon α-2a. PubMed Central, 2015
- Effects of pH, temperature, and sucrose on benzyl alcohol-induced aggregation of recombinant human granulocyte colony stimulating factor. PubMed, 2006
- Effect of antimicrobial preservatives on partial protein unfolding and aggregation. PubMed Central, 2014
Disclaimer: This content is for educational purposes only and does not constitute medical advice. Bacteriostatic water is supplied for reconstitution of substances intended for research and for use as directed by a healthcare professional. Peptides and medicines discussed here may be unlicensed in the UK or prescription-only; consult a qualified clinician before using any medicine. Baclabs does not sell peptides.