Melanotan II
Melanocortin Receptor AgonistresearchAlso known as: MT-2, MT-II, Melanotan 2
A synthetic cyclic peptide analogue of alpha-melanocyte-stimulating hormone (α-MSH) that induces skin tanning, increases libido, and reduces appetite through melanocortin receptor activation.
Overview
Melanotan II is a synthetic cyclic heptapeptide analogue of the naturally occurring alpha-melanocyte-stimulating hormone (α-MSH). Originally developed at the University of Arizona in the 1990s for the prevention of skin cancer by stimulating melanogenesis (skin darkening) without UV exposure, it was found to have potent sexual arousal and appetite-suppressing side effects. Melanotan II acts as a non-selective agonist at melanocortin receptors MC1R through MC5R, which accounts for its broad range of effects. Its tanning properties are mediated through MC1R activation on melanocytes, while its pro-sexual effects are primarily through MC3R and MC4R in the central nervous system. The closely related compound PT-141 (bremelanotide) was derived from Melanotan II research and is now FDA-approved for hypoactive sexual desire disorder in women. Melanotan II itself remains unapproved and is widely used in the tanning and biohacking communities despite safety concerns, particularly regarding its non-selective receptor activation and potential for promoting melanocytic nevi (moles) growth.
Mechanism of Action
Melanotan II acts as a non-selective agonist at melanocortin receptors (MC1R–MC5R): (1) MC1R activation on melanocytes stimulates eumelanin production, causing skin darkening without UV exposure; (2) MC3R and MC4R activation in the hypothalamus modulates sexual arousal pathways, increasing libido and erectile function; (3) MC4R activation in the hypothalamus suppresses appetite through POMC/AgRP neuronal circuits; (4) MC3R/MC4R activation modulates energy homeostasis and fat metabolism; (5) The cyclic structure provides enhanced metabolic stability and receptor binding affinity compared to linear α-MSH; (6) Crosses the blood-brain barrier to exert central nervous system effects.
Molecular Formula
C50H69N15O9
Molecular Weight
1024.18 g/mol
Sequence
Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2
Dosage Protocols
Dose Range
250mcg – 500mcg
Frequency
Once daily
Route
subcutaneous
Cycle Length
Loading: daily for 2-3 weeks, then 1-2x per week maintenance
Start with a low dose (100-250mcg) to assess tolerance due to common nausea. Minimal UV exposure enhances and accelerates tanning. Loading phase builds melanin, maintenance sustains it.
Source: Community protocols
Side Effects
| Effect | Severity |
|---|---|
| Nausea | moderate |
| Facial flushing | mild |
| Spontaneous erections | mild |
| Darkening of existing moles | moderate |
| Appetite suppression | mild |
| Fatigue / Drowsiness | mild |
| Injection site reactions | mild |
| Increased blood pressure | moderate |
Pros & Cons
Provides effective skin darkening with minimal or no UV exposure, potentially reducing UV-related skin damage
Strong pro-sexual effects including increased libido and improved erectile function in both sexes
Appetite suppression can aid in weight management goals
Once tanning is established, infrequent maintenance dosing is sufficient
Non-selective melanocortin receptor activation causes a wide range of off-target effects
May promote growth or darkening of existing moles, with theoretical concern for melanoma in predisposed individuals
Significant nausea is very common, especially at initiation
Not approved for human use in any country; quality control of research products is variable
Long-term safety data in humans is lacking
Research Studies
Legal Status
Not FDA-approved. Available as a research chemical. Illegal to sell for human consumption in many countries including Australia and the UK. Banned by WADA. PT-141, a derivative, is FDA-approved for female HSDD.
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