The questions below are the ones researchers ask most about storing, mixing and handling Melanotan II. Each answer reflects the peptide’s structure, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and links to the fuller page where there is one.
How long does Melanotan II last in the fridge after mixing?
Mixed with bacteriostatic water and kept at 2 to 8 °C in the dark, Melanotan II lasts 8 to 12 weeks under Vistara Labs’ handling guidance, with quality slowly fading from around week 6 to 8. No published study gives a refrigerated window in bacteriostatic water, so the window is general guidance that its chemistry supports. The full table is on how long Melanotan II lasts.
How long does unmixed Melanotan II powder last?
One supplier rates the sealed powder, kept away from moisture, at 1 year at minus 20 °C and 2 years at minus 80 °C, and a second rates its acetate salt at 4 years or more at minus 20 °C. Neither gives a fridge figure, so the fridge is for vials in near-term use. Days at room temperature in transit do not harm the dry cake, so it ships without an ice pack.
Why is Melanotan II more stable than most peptides?
Norleucine replaces the methionine of alpha-MSH, so the commonest oxidation route is designed out (Al-Obeidi et al., Journal of Medicinal Chemistry, 1989). It has no cysteine, asparagine or glutamine, its aspartic acid is tied into the lactam ring, and the ring plus a D-phenylalanine resist enzymes. Its developers describe it as enzymatically resistant.
What is the weak point of Melanotan II in solution?
The tryptophan. Its ring absorbs ultraviolet light and oxidises, and some of its oxidation products are yellow. The histidine is a second site, sensitive to oxidation catalysed by trace metals. Light, metals and warmth speed both, so a mixed vial is kept cold, dark and sealed. The details are on the Melanotan II stability page.
What do you mix Melanotan II with?
Bacteriostatic water, which is sterile water with 0.9% benzyl alcohol so a refrigerated vial can be accessed more than once. One supplier rates Melanotan II in water at 100 mg/mL or more. Because bacteriostatic water is unbuffered, the peptide keeps more of its positive charge than it would in neutral buffer, which helps it dissolve. The reasons are on the Melanotan II solubility guide.
How much bacteriostatic water goes in a 10 mg Melanotan II vial?
There is no single correct volume. With 2 mL a 10 mg vial gives 5 mg/mL; with 1 mL it gives 10 mg/mL. More water spreads the same amount of peptide through a larger volume, so write the chosen concentration on the vial. The tables and calculator are on the Melanotan II reconstitution page.
Why does one supplier call Melanotan II sparingly soluble?
Its sheet describes the acetate salt in phosphate-buffered saline at pH 7.2, where Melanotan II carries only one positive charge and salt screens it, so its hydrophobic residues can stack. In plain water the histidine is also charged and another supplier rates it at 100 mg/mL or more. The two figures describe different liquids; that explanation is our reading of the chemistry.
Why is my Melanotan II cloudy or tinted after mixing?
Brief cloudiness that clears within 10 to 15 minutes is usually trapped air from adding water too fast or shaking. Haze that persists usually points to the wrong diluent, such as neutral buffer. Haze, particles or a yellow tint that appear later point to warm storage, light, freezing or contamination, and the solution is discarded. More in why peptides gel or go cloudy.
Can you freeze mixed Melanotan II or the spray?
Not a vial that will be opened again, because repeated freezing and thawing promotes aggregation in peptide solutions. Laboratories that need frozen solution divide it into single-use aliquots and thaw each one once. The ready-mixed spray is never frozen. Sealed powder can be frozen at minus 20 °C without concern.
Does Melanotan II need to be kept out of the light?
Yes, more than most peptides. Tryptophan is the residue light oxidises, and Melanotan II also carries a phenylalanine. Keep the vial and the spray boxed in the main body of the fridge and return them after each access.
All products supplied by Vistara Labs are intended for laboratory research use only. They are not drugs, are not approved for human or veterinary use, and are not intended to diagnose, treat, cure or prevent any condition. Nothing on this page constitutes medical advice or guidance for use in humans.
