Overview
Melanotan II (MT-2) is a synthetic cyclic heptapeptide analog of α-melanocyte-stimulating hormone (α-MSH) developed at the University of Arizona in the 1990s. Unlike its linear predecessor Melanotan I (afamelanotide/MT-1, now FDA-approved as Scenesse® for erythropoietic protoporphyria), MT-2 is a non-selective agonist that activates multiple melanocortin receptors (MC1R, MC3R, MC4R, MC5R), producing a broader and more complex pharmacological profile.
MT-2's activation of MC1R drives melanogenesis—the production of eumelanin pigment in melanocytes—which produces a tanning effect independent of UV radiation exposure. However, its simultaneous activation of MC4R in the hypothalamus produces significant secondary effects including appetite suppression, increased sexual arousal, and penile erection. The sexual function effects led to the development of bremelanotide (PT-141/Vyleesi®), a derivative of MT-2 that was FDA-approved for hypoactive sexual desire disorder in 2019.
Despite its widespread illicit use for cosmetic tanning, MT-2 has never been approved for human use in any country. Health authorities including the FDA, TGA, and EMA have issued warnings about unregulated MT-2 products, citing concerns about contamination, melanoma risk, cardiovascular effects, and lack of quality control.
This guide examines the available research evidence, pharmacology, and safety considerations for MT-2, emphasizing the distinction between clinical research findings and unregulated consumer use.
Quick facts
- Mechanism
- Non-selective melanocortin receptor agonist stimulating melanogenesis
- Primary use
- Melanogenesis & Sexual Function
- Evidence
- moderate
- FDA
- Not approved
- Route
- Subcutaneous injection
- Typical results
- Visible tanning effects within 1–2 weeks; sexual function improvements reported within days
Chemical information
MT-2 (C₅₀H₆₉N₁₅O₉) is a hormonal compound with a molecular weight of 1024.18 g/mol. Its structural characteristics underpin its biological activity in hormonal signaling and endocrine function.
How MT-2 works
MT-2 binds to melanocortin receptors 1, 3, 4, and 5 as an agonist, triggering receptor-specific downstream signaling cascades. At MC1R on melanocytes, it activates adenylyl cyclase → cAMP → PKA → CREB → MITF transcription factor, which upregulates tyrosinase enzyme expression and eumelanin production. At hypothalamic MC4R, it modulates appetite, sexual arousal, and energy homeostasis through distinct neuronal circuits.
MC1R activation in melanocytes is the primary mechanism for MT-2's tanning effects. The cAMP-PKA-MITF signaling cascade increases transcription of three key melanogenic enzymes: tyrosinase, TRP-1, and TRP-2. These enzymes catalyze the conversion of tyrosine to eumelanin (brown-black pigment) rather than pheomelanin (red-yellow pigment), which provides superior photoprotection. Studies show that MT-2 can increase melanin production by 3–5 fold in cultured melanocytes.
MC4R activation in the paraventricular nucleus (PVN) of the hypothalamus mediates MT-2's sexual function effects through downstream oxytocin release and activation of spinal cord erectile centers. This pathway is independent of the NO-cGMP mechanism targeted by PDE5 inhibitors (e.g., sildenafil), making MT-2 effective in some cases where PDE5 inhibitors fail. The MC4R-mediated appetite suppression also involves POMC/AgRP neuron modulation in the arcuate nucleus.
MC3R activation contributes to energy homeostasis and fat metabolism regulation, while MC5R activation in sebaceous glands affects sebum production. The non-selectivity of MT-2 across these receptor subtypes produces its characteristic multi-system effects but also increases the risk profile compared to receptor-selective analogs.
- MC1R → Melanogenesis: cAMP/PKA/MITF cascade upregulates tyrosinase for eumelanin production
- MC4R → Sexual function: Hypothalamic activation triggers oxytocin-mediated erectile and arousal pathways
- MC4R → Appetite: POMC neuron activation suppresses food intake and modulates energy balance
- MC3R → Metabolism: Regulates fat storage and energy homeostasis
- MC5R → Sebaceous: Modulates sebum production in skin glands
Pharmacokinetics
| Parameter | Value | Significance |
|---|---|---|
| Molecular Weight | 1024.18 g/mol | Cyclic peptide structure enhances stability versus linear analogs |
| Half-life | ~1.5–2 hours | Short plasma half-life but melanogenesis effects persist for days |
| Bioavailability | ~75% (subcutaneous) | Good absorption from subcutaneous injection sites |
| Onset of Tanning | 3–7 days | Melanin production requires enzymatic upregulation time |
Dosing & administration
MT-2 dosing varies by indication and individual factors. No FDA-approved dosing exists for this compound; protocols in the literature derive from limited clinical or preclinical data and practitioner experience.
Any use should be conducted under qualified medical supervision with appropriate monitoring of safety markers.
Important: These dosing ranges are not FDA-approved. Any use should be under qualified medical supervision.
Side effects & safety
Safety data for MT-2 is primarily derived from preclinical studies and limited human data. Long-term effects in humans remain incompletely characterized.
Common
- • Increased skin pigmentation (tanning) without UV exposure
- • Enhanced sexual arousal and erectile function in both sexes
- • Appetite suppression and reduced food intake
- • Potential photoprotective effects through increased eumelanin
- • Led to development of FDA-approved bremelanotide (PT-141) for HSDD
Serious / potential risks
- • Nausea (very common, especially initially)
- • Facial flushing and warmth
- • Fatigue and drowsiness
- • Involuntary erections (priapism risk)
- • Darkening of existing nevi (moles)—melanoma screening concern
- • Hypertension and cardiovascular effects
- • Unregulated products carry contamination risks
Drug interactions
| Medication | Interaction | Recommendation |
|---|---|---|
| PDE5 inhibitors (Sildenafil) | Additive erectile effects | Combination significantly increases priapism risk; avoid concurrent use |
| Antihypertensives | Blood pressure fluctuation | MT-2 can raise blood pressure; monitor closely and adjust antihypertensive dosing |
| Antiemetics (Ondansetron) | Symptom management | Often used to manage MT-2-induced nausea; no pharmacological interaction |
| Immunotherapy (anti-PD-1) | Theoretical melanocyte concern | Melanocyte stimulation during immunotherapy may complicate monitoring; avoid use |
Storage & handling
Lyophilized (powder)
- • Store at -20°C to 4°C (freezer or refrigerator)
- • Protect from light and moisture
- • Stable for 12–24 months when stored properly
- • Keep in original sealed container until reconstitution
Reconstituted solution
- • Refrigerate at 2–8°C after reconstitution
- • Use bacteriostatic water for multi-dose reconstitution
- • Typical stability: 14–28 days refrigerated
- • Do not freeze reconstituted solution
Cost & availability
| Source | Cost | Notes |
|---|---|---|
| Research suppliers | Varies widely | Quality and purity vary significantly between sources |
| Compounding pharmacies | Prescription required | Higher quality assurance and purity testing |
The bottom line
MT-2 is a hormonal compound with research interest in melanocortin, tanning, sexual function, appetite. While preclinical evidence is encouraging, it remains investigational and is not FDA-approved. Any use should be under qualified medical supervision.
Best for
- • Researchers studying hormonal signaling and endocrine function
- • Individuals interested in melanocortin under medical guidance
Not for
- • Self-administration without medical supervision
- • Pregnant or breastfeeding individuals
- • Individuals with contraindicated conditions
Related compounds
Frequently asked questions
References
- [1] 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). doi: 10.1016/0024-3205(96)00191-3 PMID: 8769329
- [2] Wessells H, Fuciarelli K, Hansen J, et al.. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction. J Urol (1998). doi: 10.1016/S0022-5347(01)62879-6 PMID: 9474175
- [3] Hruby VJ, Lu D, Sharma SD, et al.. Cyclic lactam α-melanotropin analogues of Ac-Nle4-cyclo[Asp5,D-Phe7,Lys10]-α-MSH(4-10)-NH2. J Med Chem (1995). doi: 10.1021/jm00010a020 PMID: 7658432
- [4] Langan EA, Nie Z, Rhodes LE.. Melanotropic peptides: more than just 'Barbie drugs' and 'tan jabs'?. Br J Dermatol (2010). doi: 10.1111/j.1365-2133.2009.09556.x PMID: 19906072