Melanotan I vs Melanotan II
Melanotan I and Melanotan II are both synthetic analogs of alpha-melanocyte-stimulating hormone (α-MSH), but they differ significantly in receptor selectivity and effects. Melanotan I (afamelanotide) is a linear peptide that primarily activates MC1R for melanin production. Melanotan II is a cyclic peptide with broader melanocortin receptor activity, producing tanning alongside libido, appetite, and other effects. Understanding these differences is critical for research design.
TL;DR — The Verdict
Melanotan I is the safer, more selective option specifically for melanogenesis research, with actual clinical approval. Melanotan II produces stronger tanning effects and has additional sexual function and appetite applications, but comes with more side effects due to its non-selective receptor activation. For pure melanin research, MT-I is more appropriate. For multi-target research, MT-II covers more ground.
At a Glance
Melanotan I
Full profile →The linear melanocortin receptor agonist (afamelanotide)
Strengths
- + FDA-approved as Scenesse for erythropoietic protoporphyria (EPP)
- + More selective for MC1R (melanin production)
- + Implant formulation available for sustained release
- + Fewer off-target side effects than MT-II
- + Clinical trial data supporting safety
Limitations
- − Only approved for a rare condition, not general tanning
- − Weaker tanning effect per dose compared to MT-II
- − More expensive due to pharmaceutical-grade production
- − No significant appetite or libido effects
Melanotan II
Full profile →The broad melanocortin receptor agonist
Strengths
- + Stronger tanning effect per dose
- + Additional effects on libido through MC3R/MC4R activation
- + Appetite suppression properties
- + Lower cost than Melanotan I
- + Well-studied in research literature
Limitations
- − Non-selective; activates MC1R through MC5R
- − More side effects including nausea and facial flushing
- − Concerns about mole darkening and nevus changes
- − Not FDA-approved for any indication
- − WADA banned substance
Detailed Comparison
Receptor Selectivity
Melanotan I winsMelanotan I
Melanotan I preferentially activates the MC1R receptor, which is the primary receptor controlling melanin synthesis in melanocytes. This selectivity means it stimulates pigmentation with minimal activation of MC3R, MC4R, and MC5R. The result is a focused melanogenic effect without significant appetite, sexual function, or other off-target changes mediated by other melanocortin receptors.
Melanotan II
Melanotan II acts as a non-selective agonist across MC1R, MC3R, MC4R, and MC5R. MC1R activation drives tanning. MC3R and MC4R activation in the hypothalamus affects sexual arousal and appetite. MC5R has roles in sebaceous gland function. This broad activation creates a package of effects: tanning, increased libido, decreased appetite, and sometimes nausea from CNS receptor activation.
Bottom line: Melanotan I is more selective and predictable. Melanotan II hits more targets, useful for multi-outcome research but less precise.
Tanning Efficacy
Melanotan II winsMelanotan I
Melanotan I produces meaningful increases in skin pigmentation but requires higher doses and longer protocols to achieve visible tanning compared to MT-II. In clinical trials for EPP, subcutaneous implants releasing afamelanotide over 60 days produced significant skin darkening and UV protection. The effect is gradual and uniform, building over weeks.
Melanotan II
Melanotan II produces faster and more intense tanning at lower doses. Users typically report visible skin darkening within 1-2 weeks of beginning administration. The cyclic structure gives it higher potency at MC1R despite being less selective overall. However, the tanning can be uneven, and there are concerns about asymmetric darkening of existing moles and nevi.
Bottom line: MT-II tans faster and stronger per dose. MT-I tans more gradually and uniformly. MT-II carries additional concerns about mole changes.
Sexual Function Effects
Melanotan II winsMelanotan I
Melanotan I has no clinically significant effects on sexual function. Its selectivity for MC1R means it largely bypasses the MC3R and MC4R receptors responsible for melanocortin-mediated sexual arousal. This is actually an advantage for research specifically focused on melanogenesis without confounding sexual function variables.
Melanotan II
Melanotan II has well-documented pro-sexual effects through MC3R and MC4R activation. These effects led to the development of PT-141 (bremelanotide), which is essentially a metabolite of MT-II that was isolated specifically for sexual function. MT-II can cause spontaneous erections and increased libido in both male and female subjects, which is the primary reason many seek it outside of tanning.
Bottom line: MT-II has significant sexual function effects. MT-I has none. For sexual function research, PT-141 (derived from MT-II) is now the dedicated compound.
Safety Profile
Melanotan I winsMelanotan I
Melanotan I has undergone formal clinical trials and received regulatory approval (EMA-approved, FDA-approved for EPP). The safety profile is well-characterized through controlled studies. Side effects include headache, nausea, and localized implant site reactions. No concerning patterns of mole changes or melanoma risk have been identified in clinical surveillance.
Melanotan II
Melanotan II has not undergone the same level of regulatory scrutiny. Common side effects include nausea (especially initial doses), facial flushing, fatigue, and appetite suppression. More concerning are reports of mole darkening and changes in nevus morphology, which raise theoretical concerns about melanocyte stimulation in pre-existing lesions. Long-term safety data from controlled studies is lacking.
Bottom line: MT-I has a formally validated safety profile through regulatory approval. MT-II lacks this validation and carries additional concerns about mole changes.
Who Should Choose What?
Choose Melanotan I if:
- → Research focused specifically on melanogenesis
- → Protocols requiring regulatory-grade safety data
- → Studies on UV protection and photoprotection
- → Erythropoietic protoporphyria research
- → Protocols where sexual function effects are confounding
Choose Melanotan II if:
- → Research on broad melanocortin system activation
- → Studies involving both pigmentation and sexual function
- → Appetite and metabolism research
- → Cost-sensitive research protocols
- → Studies requiring faster onset of pigmentation
Ready to Calculate Your Protocol?
Use our dosing and reconstitution calculators pre-loaded with Melanotan I or Melanotan II values.
Research & Educational Use Only
All content is for informational and research purposes only. This site does not provide medical advice, diagnosis, or treatment. Consult a qualified healthcare professional before using any peptide or supplement.
The information presented here is compiled from published research studies and is intended for informational purposes only. Individual results may vary. Always consult with a licensed healthcare provider.