Summary

Melanotan II (MT-II) is a synthetic analogue of alpha-melanocyte-stimulating hormone (α-MSH) that acts on melanocortin receptors to stimulate melanin production (skin tanning), suppress appetite, and enhance libido. Developed in the 1990s at the University of Arizona, it has been researched for skin cancer prevention and sexual dysfunction. It has never been approved as a licensed medicine and carries notable safety concerns including the MHRA issuing public warnings about its unlicensed use.

Overview

Melanotan II (MT-II) is a synthetic analogue of alpha-melanocyte-stimulating hormone (α-MSH), a naturally occurring hormone that acts on melanocortin receptors in the body. It was originally developed at the University of Arizona in the 1990s by researchers led by Victor Hruby and Mac Hadley, as part of research into skin cancer prevention through melanin stimulation.

MT-II activates several melanocortin receptor subtypes (MC1R, MC3R, MC4R, MC5R), which produces a range of effects: increased melanin production (skin darkening), appetite suppression, and increased libido and erectile function. This multi-receptor activity is both why the peptide is of research interest and why its side-effect profile is broader than more selective analogues.

A related compound, Melanotan I (afamelanotide, Scenesse®), is a licensed medicine in Europe for the treatment of erythropoietic protoporphyria (EPP), a rare light-sensitive skin condition. Melanotan II is distinct from afamelanotide — it is shorter, more potent, and acts on more receptor subtypes.

Research Summary

Tanning and Skin Pigmentation

The primary research application of MT-II is stimulation of melanogenesis (melanin production) without UV exposure. A 2003 study by Dorr et al. demonstrated that MT-II administration increased skin melanin density in human volunteers, providing a tanning effect (Dorr et al., 2003).

Sexual Function

A notable finding in the clinical research was MT-II's effect on erectile function. A 2000 pilot study by Wessells et al. found that MT-II induced erections in men with erectile dysfunction (Wessells et al., 2000). This led to the development of bremelanotide (PT-141), a derivative of MT-II that acts more selectively on MC4R and has received FDA approval as Vyleesi® for premenopausal hypoactive sexual desire disorder (HSDD).

Safety Concerns

MT-II has been associated with a range of side effects, including nausea, flushing, spontaneous erections (priapism in some cases), darkening of existing moles and freckles, and emergence of new naevi. The MHRA issued warnings about Melanotan products in 2008 and again in subsequent years, noting they are unlicensed medicines and that adverse reactions had been reported through the Yellow Card scheme.

A 2019 review by Evans-Brown et al. in the Journal of the Royal Society of Medicine catalogued adverse events associated with Melanotan use, including melanoma concerns, though causality has been difficult to establish (Evans-Brown et al., 2019).

Limitations

MT-II has not been approved as a medicine in any country. Clinical trial data is limited to early-phase studies. The long-term safety of MT-II use has not been established, and regulatory bodies globally have warned against its unlicensed use.

Commonly Discussed Protocols

Note: The following describes protocols commonly discussed in research communities. This is not medical advice. Melanotan II is sold for research use only and is not a licensed medicine.

  • Subcutaneous injection: Commonly discussed doses range from 250–500 micrograms (mcg) per day, with some protocols starting at a lower dose (100–250 mcg) to assess tolerance.
  • Loading phase: Typically 10–14 days of daily dosing, intended to build melanin levels.
  • Maintenance phase: 1–2 injections per week after the loading period.
  • UV exposure: Some protocols combine MT-II with low-dose UV exposure (sunbeds or sunlight), based on the theory that UV + melanocyte stimulation accelerates tanning. This raises additional safety considerations.

Stacking

MT-II is generally used as a standalone compound. Some research discussions mention combining it with:

  • Vitamin D supplementation: To support overall skin health during UV exposure. No specific evidence supports or refutes this combination.

Storage & Reconstitution

  • Lyophilised powder: Store at -20°C for long-term storage, or 2–8°C for short-term use. Protect from light.
  • Reconstitution: Reconstitute with bacteriostatic water. Gently swirl — do not shake.
  • Reconstituted solution: Store at 2–8°C and use within 28–30 days. Protect from light, as the peptide may degrade with prolonged light exposure.

Blood Work

While MT-II is not typically associated with systemic hormonal disruption, researchers monitoring its use may consider:

  • Full blood count — to monitor general health status
  • Liver function tests — as with any peptide administered systemically
  • Dermatological monitoring — regular skin checks to monitor changes in existing moles and the appearance of new naevi are strongly recommended

UK Legal Status

Melanotan II is not a licensed medicine in the UK and is not approved by the MHRA. The MHRA has issued explicit public warnings about Melanotan products, stating they are unlicensed medicines and that their safety has not been established. The MHRA has noted adverse reaction reports received via the Yellow Card scheme.

Melanotan II is not listed under the Misuse of Drugs Act and is not a controlled substance. However, selling Melanotan II for human consumption would violate MHRA medicines regulations. It is sold by some vendors as a 'research chemical', though this framing has been challenged by regulatory authorities.

Researchers should be aware that the MHRA has taken enforcement action against vendors selling Melanotan products.

References

  1. Dorr RT, et al. "Evaluation of Melanotan-II, a Superpotent Cyclic Melanotropic Peptide in a Phase I Clinical Study." Life Sciences. 2003; 73(6): 779-792. DOI: 10.1016/S0024-3205(03)00390-5
  2. Wessells H, et al. "Effect of Melanotan-II, a Melanocortin Receptor Agonist, on Erectile Function." International Journal of Impotence Research. 2000; 12 Suppl 4: S74-S79.
  3. Evans-Brown M, et al. "Melanotan Use in the United Kingdom." Journal of the Royal Society of Medicine. 2019.
  4. MHRA. "Melanotan — Unlicensed Medicine Warning." MHRA Drug Safety Update, 2008.
  5. Hadley ME, Hruby VJ. "Melanotan-II: Discovery and Early Development." Annals of the New York Academy of Sciences. 1999.

References

  1. Dorr RT, et al. "Evaluation of Melanotan-II, a Superpotent Cyclic Melanotropic Peptide in a Phase I Clinical Study." Life Sciences. 2003; 73(6): 779-792. DOI: 10.1016/S0024-3205(03)00390-5
  2. Wessells H, et al. "Effect of Melanotan-II, a Melanocortin Receptor Agonist, on Erectile Function." International Journal of Impotence Research. 2000; 12 Suppl 4: S74-S79.
  3. Evans-Brown M, et al. "Melanotan Use in the United Kingdom." Journal of the Royal Society of Medicine. 2019.
  4. MHRA. "Melanotan — Unlicensed Medicine Warning." MHRA Drug Safety Update, 2008.
  5. Hadley ME, Hruby VJ. "Melanotan-II: Discovery and Early Development." Annals of the New York Academy of Sciences. 1999.