Melanotan II (MT-2) Pen
10 mg of the cyclic lactam alpha-MSH analogue in 3 mL of bacteriostatic water, about 3.33 mg/mL. Filled from a peptide lot tested in the manufacturer’s own laboratory, with a certificate.
| Compound | Melanotan II (acetate) Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH₂; supplied as the acetate salt, values quoted for the free peptide |
|---|---|
| CAS number | 121062-08-6 |
| Molecular formula | C50H69N15O9 |
| Theoretical mass | 1024.2 Da |
| Sequence / structure | Ac-Nle-cyclo[D-H-[D-Phe]-R-W-K]-NH₂ (7 residues; Asp–Lys side-chain lactam; N-acetyl; C-terminal amide) |
| Contents | Melanotan II (acetate): 10 mg per 3 mL pen (0.33% w/v) |
| Form | Sterile aqueous solution in bacteriostatic water (0.9% benzyl alcohol), supplied in a 3 mL glass cartridge inside a preloaded autoinjector pen fitted with a needle |
| Storage, sealed | Store at 2–8 °C in the original carton, protected from light |
| Format | Solution in a 3 mL pre-filled pen |
Sizes and lots
- 10 mg · 1 pen — $68.99
- 10 mg · Kit of 10 — $613.32
Melanotan II is a cyclic seven-residue analogue of alpha-MSH, closed by a lactam bridge and amidated at its C-terminus, that acts at several melanocortin receptors. This preloaded pen holds 10 mg of melanotan II dissolved in 3 mL of bacteriostatic water, about 3.33 mg/mL, so there is no powder to make up. The published work on the peptide is small: preformulation chemistry, two small human studies reported in 1996 and 2000, and a run of case reports tied to products sold online.
What is in the pen
The 3 mL glass cartridge holds a sterile aqueous solution. The safety data sheet lists melanotan II at 0.33% w/v, 10 mg per pen, in bacteriostatic water with 0.9% benzyl alcohol as an antimicrobial preservative. The peptide is the acetate salt of Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, the same compound as the MT-2 10 mg vial, with figures quoted for the free peptide (1024.2 Da). On that basis the pen holds about 9.8 µmol, roughly 3.3 mM. The SDS does not classify the peptide; benzyl alcohol is listed as harmful if swallowed or inhaled, a serious eye irritant and a skin sensitiser.
Keep the pen at 2 to 8 °C in its carton, protected from light, and capped once opened. It must not be frozen, and a pen whose solution has frozen, discoloured or clouded should be discarded. The peptide pen vs vial article sets out how the two formats differ.
What the research covers
In its first human study melanotan II was described as a lactam-bridged cyclic heptapeptide with superpotent melanotropic activity in vitro1. That pilot trial in three healthy men also recorded nausea, somnolence and a stretching and yawning complex1. Lan and colleagues characterised the molecule's ionisation in 1994, estimating the pKa of its histidine at 6.54 and its arginine at 11.722, so its charge in solution shifts around neutral pH.
The safety literature is mostly about material bought online. Nelson and colleagues reported a man who developed sympathomimetic toxicity and rhabdomyolysis after using melanotan II bought on the internet to darken his skin, with tachycardia, raised creatinine and creatine kinase that kept climbing after admission to intensive care3.
None of the cited papers measured how long melanotan II stays intact in solution, in bacteriostatic water or otherwise, so the storage limits on the safety data sheet are the ones to follow. The full literature, including the pigmentation and erection studies and the regulatory record, is in the melanotan 1 vs melanotan 2 guide.
Frequently asked questions
How does the pen differ from the MT-2 vial?
The vial holds 10 mg of freeze-dried melanotan II acetate kept at −20 °C. The pen holds the same 10 mg already in 3 mL of bacteriostatic water and is kept at 2 to 8 °C. The vial leaves the concentration to the laboratory; the pen fixes it at about 3.33 mg/mL.
Has melanotan II been studied in solution?
Only indirectly. Preformulation work measured its dissociation constants and partition coefficient, but none of the papers on this page tracked its stability in bacteriostatic water over time. The SDS conditions, 2 to 8 °C, dark and never frozen, are what the pen should be kept under.
References
- Dorr RT, Lines R, Levine N, et al. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sci. 1996;58(20):1777-84. DOI · PubMed
- Lan EL, Ugwu SO, Blanchard J, et al. Preformulation studies with melanotan-II: a potential skin cancer chemopreventive peptide. J Pharm Sci. 1994;83(8):1081-4. DOI · PubMed
- Nelson ME, Bryant SM, Aks SE. Melanotan II injection resulting in systemic toxicity and rhabdomyolysis. Clin Toxicol (Phila). 2012;50(10):1169-73. DOI · PubMed
For laboratory research use only. Not for human or veterinary consumption. Products have not been evaluated by the U.S. Food and Drug Administration and are not intended to diagnose, treat, cure or prevent any disease.