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Melanocortin System

Melanotan II

Unapproved synthetic tanning peptide that also boosts libido and suppresses appetite; notable nausea, BP and mole risks.

RestrictedEvidence level 3 of 5: Limited human dataAlso: MT-II, MT2, Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2

Overview

Melanotan II is a synthetic, ring-shaped seven-amino-acid analog of α-MSH developed at the University of Arizona in the 1990s as a 'sunless tan' agent. Because it activates several melanocortin receptors at once, it darkens skin through MC1R and also increases sexual arousal and reduces appetite through MC3R and MC4R in the brain. Its libido effect led directly to the development of bremelanotide (PT-141). Melanotan II itself was never developed into an approved medicine and is sold mostly through unregulated online channels with variable purity. Nausea, flushing and blood-pressure changes are common, priapism has been reported, and multiple case reports describe rapidly changing moles and melanoma, so dermatology supervision is essential if it is used at all.

Classification
Synthetic cyclic heptapeptide, non-selective melanocortin receptor agonist
Route
Subcutaneous (intranasal products exist but are unreliable)
Half-life
~30–45 minutes (SC); effects last hours

Mechanism of action

Primary targetNon-selective agonist at MC1R, MC3R, MC4R and MC5R
  1. Subcutaneous injectionCyclic structure resists breakdown, extending action versus native α-MSH.
  2. MC1R activationMelanocytes switch to eumelanin production, darkening skin.
  3. Central MC4R activationHypothalamic and spinal pathways increase sexual arousal and erections.
  4. MC3R/MC4R appetite effectsSatiety signaling increases, reducing food intake.
  5. Off-target autonomic effectsNausea, flushing and blood-pressure changes reflect broad receptor activation.
Downstream effects
  • Skin tanning
  • Increased libido
  • Appetite suppression

Researched for

  • Sunless tanning and photoprotection
  • Erectile dysfunction
  • Sexual arousal
  • Appetite and weight control

Research notes

  • Dorr et al. (1996) Phase 1: tanning in healthy men at low doses, with nausea and spontaneous erections.
  • Wessells et al. (1998, 2000): small crossover trials showed erections in men with psychogenic and organic ED.
  • Case reports describe eruptive nevi, changing moles and melanoma in users.
  • No long-term human safety studies; unregulated products vary in purity and dose.

Reported side effects

  • Nausea (common, dose-limiting)
  • Facial flushing
  • Darkening or new moles and freckles
  • Spontaneous erections; priapism (rare)
  • Blood-pressure changes

Contraindications & cautions

  • Personal or family history of melanoma
  • Atypical/dysplastic nevus syndrome or many moles
  • Uncontrolled hypertension or recent cardiovascular event
  • History of priapism
  • Pregnancy and breastfeeding

Lab monitoring

  • CBC, CMP
  • Blood pressure (baseline and every 2 weeks)
  • Baseline dermatology full-skin exam with mole mapping
  • Dermatology follow-up every 4–6 weeks during use
  • Vitamin D (25-OH)

Dosing and pricing for Melanotan II

Dosing references and compound pricing are available to established patients in the secure portal after a medical evaluation.

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