PT-141 is a synthetic peptide that comes as a white lyophilised powder — freeze-dried to remove all water. Store it in a freezer at -20 °C and it stays stable for two or more years. Once reconstituted, move it to the fridge at 2–8 °C and use it within four to eight weeks.
Those are the numbers that matter most. Everything below explains the why behind them and what to look for on a certificate of analysis.
What Is PT-141 Peptide
PT-141 is a synthetic melanocortin peptide. Its chemical name is bremelanotide. It was developed from a compound called Melanotan II during earlier research programmes.
It is a cyclic heptapeptide — a chain of seven amino acids arranged in a ring. That ring structure makes it more resistant to breakdown than a straight-chain peptide of similar size, which is one reason its shelf life is relatively long when stored correctly.
What Is PT-141 10mg
The 10 mg figure is the amount of lyophilised peptide in a single vial. Ten milligrams is a common research quantity. You will also see 5 mg vials. The number tells you how much powder is present before reconstitution, not the concentration of the final solution — that depends on how much bacteriostatic water you add.
If you add 1 mL of water to a 10 mg vial, you get a 10 mg/mL solution. Add 2 mL and you get 5 mg/mL. Neither is wrong — the volume you choose sets the concentration you work with.
PT-141 Lyophilised Storage
Lyophilised PT-141 powder should be kept at -20 °C, away from light and moisture. Freeze-drying removes virtually all water from the peptide, which is what gives it that long shelf life. Without water, the chemical reactions that break peptides down slow to almost nothing.
A few practical points for storing the powder:
- Keep vials sealed and upright
- Avoid repeated freeze-thaw cycles — each one adds a small amount of stress to the peptide structure
- Let a vial warm to room temperature before opening it, so condensation forms on the outside of the vial rather than inside
- Do not leave powder vials at room temperature for extended periods; even dry peptides degrade faster above 8 °C
If your freezer runs at -80 °C, that is better still for long-term archival storage. But -20 °C is fine for working stock you plan to use within a year or two.
PT-141 Storage After Reconstitution
Once you add bacteriostatic water, PT-141 solution goes in the refrigerator at 2–8 °C — not back in the freezer. Freezing a reconstituted peptide solution can damage the peptide through ice crystal formation, and bacteriostatic water is not designed to be frozen.
Expect four to eight weeks of usable stability in the fridge. Bacteriostatic water contains 0.9% benzyl alcohol, which slows microbial growth, but it does not stop chemical breakdown of the peptide itself. The clock starts the moment you add water.
Label every vial with the reconstitution date. It takes ten seconds and removes all guesswork.
PT-141 COA: What to Look For
A COA — certificate of analysis — is the test report that confirms what is actually in the vial. A legitimate PT-141 COA should include:
- Identity confirmation: usually mass spectrometry (MS), which checks the molecular weight matches PT-141 (molecular weight 1025.2 g/mol)
- Purity: shown as a percentage, typically from HPLC testing — high-performance liquid chromatography, a method that separates and quantifies compounds in a mixture. Research-grade material is generally 98% or higher
- Sequence confirmation: verifies the correct amino acids are present in the correct order
- Appearance: should read as white to off-white lyophilised powder
- Water content: low residual moisture, often below 8%, confirms the freeze-drying worked properly
The COA should name the testing lab and show a batch or lot number that matches the vial. If the batch number on the vial and the COA do not match, the document is not yours.
Summary
PT-141 is a cyclic seven-amino-acid peptide supplied as a freeze-dried powder. Store the powder at -20 °C, sealed and away from light, and it is stable for two or more years. Reconstitute with bacteriostatic water and refrigerate at 2–8 °C — use within four to eight weeks and label the vial. Before you open anything, check the COA for matching batch numbers, an HPLC purity of 98%+ and a mass spec identity confirmation.
NXT Labs products are sold strictly as research chemicals for in vitro research, laboratory testing and analytical purposes only, and are not intended for use in any human or animal application.
NXT Labs supplies research peptides for laboratory use. Browse the full range or view current Certificates of Analysis.
