Quick answer
How is tesamorelin reconstituted and stored? Keep the lyophilized vial at −20 °C (or 2–8 °C for short-term use), protected from light and moisture. To reconstitute, warm the sealed vial to room temperature, add bacteriostatic water slowly down the glass wall, and roll gently until clear; do not shake. A 10 mg vial with 2 mL of diluent gives 5 mg/mL. Refrigerate the solution at 2–8 °C and use it within about 28 days, or sooner for sensitive assays. For stocks needed longer, freeze single-use aliquots.
Tesamorelin is a comparatively long synthetic peptide, and long peptides give degradation chemistry more places to act. Careful handling is therefore not a formality: it is what keeps the concentration written on your tube equal to the concentration in it. This guide explains tesamorelin's stability profile, gives a reconstitution protocol for controlled laboratory work, provides worked concentration and molarity tables for the 10 mg vial, and lists the handling errors that most often compromise results. For laboratory research use only; not for human consumption.
Why proper handling matters
Experimental reproducibility depends on knowing how much intact peptide is present. Degradation does not usually announce itself. A solution containing 15% oxidized or aggregated tesamorelin looks identical to a fresh one, yet a receptor assay run with it will report a shifted response that can be mistaken for a biological effect. Controlling storage and reconstitution removes that source of noise before it reaches the data.
Understanding tesamorelin's stability profile
Tesamorelin consists of the full 44-amino-acid sequence of human growth hormone-releasing hormone, GHRH(1-44) amide, with a trans-3-hexenoyl group attached to the N-terminal tyrosine. That small hydrophobic cap was introduced to protect the N-terminus from enzymatic cleavage by dipeptidyl peptidase-4. The molecular formula is C221H366N72O67S and the molecular weight is approximately 5,135.9 g/mol.
| Property | Value | Handling implication |
|---|---|---|
| Length | 44 residues plus N-terminal acyl group | More sites for hydrolysis and deamidation than short peptides |
| Molecular weight | ≈ 5,135.9 g/mol | Use for mass-to-molar conversion |
| Methionine | One (position 27) | Oxidation risk; limit air exposure and light |
| Cysteine | None | No disulfide scrambling to manage |
| Asparagine, glutamine, aspartate | Several | Deamidation and isomerization in solution over time |
| Net character | Basic (multiple arginine and lysine residues) | Dissolves readily in water or mildly acidic diluent |
The methionine residue
Methionine's thioether side chain oxidizes to methionine sulfoxide on contact with dissolved oxygen, peroxides or light-generated radicals. Oxidation at Met27 is a well-recognized liability of GHRH-family peptides. In practice this means minimizing headspace exchange (do not repeatedly vent the vial with air), keeping the solution cold and dark, and avoiding diluents or plastics that may carry trace peroxides.
No disulfide bonds
Because the sequence contains no cysteine, there are no disulfide bridges to break, reduce or shuffle. This simplifies handling: reducing agents are unnecessary, and the peptide's conformation is not locked by covalent crosslinks that could mis-form.
Peptide bond hydrolysis and deamidation
Water slowly cleaves amide bonds and converts asparagine and glutamine side chains to their acid forms. Both reactions are accelerated by heat and by pH extremes. They are the main reason reconstituted solutions carry a far shorter working window than dry powder.
Aggregation
GHRH analogs can self-associate, particularly at higher concentrations, at neutral to basic pH, and when agitated. Aggregates reduce the effective monomer concentration and can be invisible until they are large. Gentle mixing and moderate stock concentrations limit the risk.
Lyophilized storage: the starting point
Storage temperature for lyophilized tesamorelin
| Storage duration | Recommended temperature | Notes |
|---|---|---|
| In transit (days) | Ambient | Acceptable for sealed, dry vials |
| Up to about 3 months | 2–8 °C | Keep boxed, away from the refrigerator door |
| 3 months to 2 years | −20 °C | Standard long-term condition |
| Archival reference material | −20 °C to −80 °C | Sealed secondary container with desiccant |
For context, the manufacturer's labeling for the approved, formulated tesamorelin product has specified refrigerated storage for one presentation and controlled room temperature for a later presentation, both protected from light, and instructs that the solution be used immediately after reconstitution. Those instructions apply to that specific excipient-containing formulation and should not be assumed to transfer to research-grade material, but they illustrate two points that do generalize: the dry state is robust, and the reconstituted state is not intended for prolonged holding without a preservative.
Protecting from moisture and light
Keep vials sealed until use, store them in their carton or an opaque box, and always allow a cold vial to reach room temperature before opening so that condensation does not form inside. Humidity absorbed by the cake restarts the very reactions that freeze-drying was meant to stop.
Reconstitution protocol for laboratory use
Step 1: Bring the vial to room temperature
Leave the sealed vial on the bench for 15–30 minutes. Verify the lot number against the certificate in our COA library while you wait.
Step 2: Select the diluent
| Diluent | Best suited to | Consideration |
|---|---|---|
| Bacteriostatic water (0.9% benzyl alcohol) | Multi-use stock vials held at 2–8 °C | Preservative suppresses microbial growth between punctures; benzyl alcohol may be unsuitable for some cell-based assays at high final concentrations |
| Sterile water | Single-session use or immediate aliquoting | No preservative; do not keep as a multi-use vial |
| Dilute acetic acid (0.1%) | Stocks that resist dissolving | Mildly acidic pH favors solubility of basic peptides; confirm assay compatibility |
| Buffered saline or culture medium | Final working dilutions only | Dilute from a water stock immediately before use rather than storing in buffer |
Step 3: Add diluent slowly
Swab the stoppers, draw the planned volume, and let it run down the inner wall of the vial. Do not aim the stream at the cake.
Step 4: Roll gently — do not shake or vortex
Roll the vial between your fingers or swirl it for about 30 seconds. Shaking generates foam and air–liquid interfaces that drive aggregation and expose methionine to oxygen.
Step 5: Inspect for complete dissolution
The solution should be clear and colorless with no particles. If small fragments remain, let the vial rest for a few minutes and roll again. A solution that stays cloudy should not be used for quantitative work.
Step 6: Record the working concentration
Label the vial with date, diluent, volume added and mg/mL, then refrigerate. The next section gives the numbers.
Concentration calculations: a practical reference
Concentration (mg/mL) = peptide mass (mg) ÷ diluent volume (mL). The table shows the 10 mg vial across common volumes, with the mass contained per graduation on a U-100 laboratory syringe (100 units = 1 mL, so 1 unit = 0.01 mL).
| Diluent added | Concentration | Mass per 1 unit (0.01 mL) | Mass per 10 units (0.1 mL) | Units holding 1 mg |
|---|---|---|---|---|
| 1 mL | 10 mg/mL | 100 mcg | 1,000 mcg | 10 units |
| 2 mL | 5 mg/mL | 50 mcg | 500 mcg | 20 units |
| 2.5 mL | 4 mg/mL | 40 mcg | 400 mcg | 25 units |
| 3 mL | 3.33 mg/mL | 33.33 mcg | 333 mcg | 30 units |
| 4 mL | 2.5 mg/mL | 25 mcg | 250 mcg | 40 units |
| 5 mL | 2 mg/mL | 20 mcg | 200 mcg | 50 units |
For any other volume, use the reconstitution calculator.
Mass to molar conversion
| Mass concentration | Molar concentration (MW ≈ 5,135.9 g/mol) |
|---|---|
| 10 mg/mL | ≈ 1.95 mM |
| 5 mg/mL | ≈ 974 µM |
| 2 mg/mL | ≈ 389 µM |
| 1 mg/mL | ≈ 195 µM |
| 0.1 mg/mL | ≈ 19.5 µM |
Worked dilution example
To prepare 1 mL of a 10 µM working solution from a 5 mg/mL (≈ 974 µM) stock, apply C1V1 = C2V2: V1 = (10 µM × 1,000 µL) ÷ 974 µM ≈ 10.3 µL of stock, made up to 1,000 µL with assay buffer. For nanomolar concentrations, make an intermediate dilution first (for example 1:100 to ≈ 9.74 µM) rather than pipetting sub-microliter volumes. These figures assume 100% peptide content; for exact work, correct using the net peptide content and purity on the batch COA, as explained in understanding HPLC purity.
Post-reconstitution stability and storage
Short-term use (within 24–72 hours)
For the most demanding quantitative work, prepare the solution fresh and use it within one to three days at 2–8 °C. This mirrors the conservative approach in manufacturer labeling for the formulated product and leaves the least room for oxidation or deamidation to accumulate.
Multi-use refrigerated stock
When reconstituted with bacteriostatic water and kept at 2–8 °C in the dark, a working window of up to about 28 days is the accepted convention. That number comes from the standard for preserved multi-use containers (antimicrobial effectiveness under USP <51> and beyond-use dating under USP <797>), not from a tesamorelin-specific stability study, so it is a ceiling. Given the methionine residue, many labs choose to finish a tesamorelin vial within two to three weeks.
Longer-term storage of reconstituted stock
Divide the stock into single-use aliquots in low-protein-binding tubes, freeze at −20 °C or −80 °C, and thaw each once. Filling tubes to leave minimal headspace reduces oxygen exposure.
Freeze–thaw cycle limits
Each cycle subjects the peptide to ice-interface stress and transient concentration extremes. Limit any tube to a single thaw; if a second is unavoidable, record it. Never refreeze a multi-use vial of bacteriostatic-water stock as a routine practice.
| Condition | Working window | Comment |
|---|---|---|
| Sterile water, 2–8 °C | Same day | Discard remainder |
| Bacteriostatic water, 2–8 °C | Up to ~28 days (2–3 weeks preferred) | Dark, upright, minimal warm time |
| Any diluent, room temperature | Bench handling only | Return to cold promptly |
| Aliquots, −20 °C | 1–3 months | One thaw |
| Aliquots, −80 °C | Up to ~6 months | One thaw |
Common handling errors and how to avoid them
| Common error | Consequence | Prevention |
|---|---|---|
| Opening a cold vial | Condensation wets the cake | Equilibrate sealed for 15–30 minutes |
| Shaking or vortexing | Foam, aggregation, oxidation | Roll or swirl gently |
| Storing stock in culture medium or buffer | Faster degradation; microbial growth | Store in water; dilute into buffer at time of use |
| Repeated freeze–thaw | Progressive loss of intact peptide | Single-use aliquots |
| Leaving the vial under bench lights | Photo-oxidation | Keep boxed or foil-wrapped |
| Very dilute storage stocks | Adsorption to container walls | Store at ≥ 1 mg/mL; use low-bind plastic |
| Unlabeled vials | Unknown age and concentration | Date and label at reconstitution |
| Reusing needles | Contamination and stopper coring | New sterile needle for each entry |
Connecting storage to research quality
Good storage practice only preserves what was in the vial to begin with. Start from material with lot-matched HPLC and mass-spectrometry documentation, record handling at each step, and when a result is unexpected, check the reagent before reinterpreting the biology. Guidance on sourcing is in where to buy tesamorelin, and background on the compound is in tesamorelin preclinical research.
Summary
Store tesamorelin dry, cold and dark. Reconstitute gently with a diluent chosen for how the vial will be used, calculate and label the concentration, refrigerate, and respect the working window. Aliquot for anything longer. Further reading: how to mix peptides with bacteriostatic water, storing research peptides and bacteriostatic water explained.
References
- Theratechnologies Inc. EGRIFTA SV (tesamorelin) prescribing information. U.S. Food and Drug Administration label.
- United States Pharmacopeia. General Chapter <797> Pharmaceutical Compounding—Sterile Preparations. USP–NF.
- United States Pharmacopeia. General Chapter <51> Antimicrobial Effectiveness Testing. USP–NF.
- Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544-575.
- Manning MC, Patel K, Borchardt RT. Stability of protein pharmaceuticals. Pharm Res. 1989;6(11):903-918.
- Wang W. Instability, stabilization, and formulation of liquid protein pharmaceuticals. Int J Pharm. 1999;185(2):129-188.
- Wang W. Lyophilization and development of solid protein pharmaceuticals. Int J Pharm. 2000;203(1-2):1-60.
- Goebel-Stengel M, Stengel A, Taché Y, Reeve JR Jr. The importance of using the optimal plasticware and glassware in studies involving peptides. Anal Biochem. 2011;414(1):38-46.
Frequently Asked Questions
How much bacteriostatic water should I add to a 10 mg tesamorelin vial?
It depends on the concentration you want. Adding 2 mL gives 5 mg/mL, 1 mL gives 10 mg/mL and 5 mL gives 2 mg/mL. At 5 mg/mL, each unit mark on a U-100 syringe scale holds 50 mcg.
How long is reconstituted tesamorelin stable in the refrigerator?
In bacteriostatic water at 2–8 °C and protected from light, the conventional maximum is about 28 days. Because tesamorelin contains an oxidation-prone methionine, finishing the vial within two to three weeks, or preparing fresh solution for sensitive assays, is a prudent choice.
Should lyophilized tesamorelin be kept in the fridge or the freezer?
Use the freezer at −20 °C for storage beyond roughly three months and the refrigerator at 2–8 °C for shorter periods. In both cases keep the vial sealed, boxed and dry.
Can I shake the vial to dissolve tesamorelin faster?
No. Shaking produces foam and exposes the peptide to air–liquid interfaces, encouraging aggregation and methionine oxidation. Roll or swirl gently and allow a few minutes for the cake to dissolve.
What should reconstituted tesamorelin look like?
Clear and colorless, with no visible particles. Persistent haze, fibers, color or a film on the glass indicates the solution should not be used.
Can tesamorelin be reconstituted with sterile water instead of bacteriostatic water?
Yes, and sterile water is appropriate when the solution will be used immediately or aliquoted and frozen. It contains no preservative, so it should not be held as a multi-use vial.
Is it acceptable to freeze reconstituted tesamorelin?
Yes, as single-use aliquots in low-bind tubes at −20 °C or −80 °C, thawed once. Avoid repeated freeze–thaw cycles of the same tube or of the working vial.
Why does tesamorelin need protection from light?
Light promotes oxidation of methionine and aromatic residues. Keeping the vial in its box or wrapped in foil removes an avoidable source of degradation.
How do I convert tesamorelin mg/mL to micromolar?
Divide the concentration in mg/mL by the molecular weight (about 5,135.9 g/mol) and multiply by 1,000,000. For example, 1 mg/mL is about 195 µM and 5 mg/mL is about 974 µM, before correcting for net peptide content.
Does the 28-day guideline come from tesamorelin stability data?
No. It derives from the standard applied to preserved multi-use containers under USP chapters on antimicrobial effectiveness and sterile preparations. It limits microbiological risk and serves as a conservative ceiling rather than a measured chemical shelf life.