Melanotan II

How it works

• In lab tests with human receptors, it binds several melanocortin receptors at once: MC1, MC3, MC4 and MC5.
• MC1 receptors sit on the skin's pigment cells. In the first human study, two of three men had darker skin a week after their last dose.
• Its effect on erections is thought to run through brain MC3 and MC4 receptors, with MC4 the main one. Erections came without sexual stimulation, often after yawning and stretching.
• In mice, melanotan II injected into the brain cut food intake, and a drug blocking MC3 and MC4 receptors stopped the effect.
• Bremelanotide (PT-141) is the same molecule except at one end, which carries a free acid instead of an amide.

Evidence

Caveats

• Most safety information comes from case reports, usually involving products bought online whose content and strength were uncertain.
• Nausea and yawning were common in the trials. In one, nausea was severe after 4 of 19 injections.
• Case reports describe new or darkening moles, one within a day of a single injection, and melanoma in people who had used it. A 2017 review found four melanoma reports after melanotan use but said conclusive evidence of a link is lacking.
• Other case reports describe a prolonged, painful erection (priapism) that needed surgery, and muscle breakdown (rhabdomyolysis) with kidney injury.
• In one lab analysis, online vials held 43% to 88% of the labelled amount, and some contained unknown impurities.
• Claims that it protects against skin cancer have no human outcome data behind them.
• There is no formal list of contraindications. The case reports support caution in anyone with a history of melanoma or unusual moles.

References

1. Dorr RT, et al. Life Sci. 1996;58:1777-1784.
2. Wessells H, et al. J Urol. 1998;160:389-393.
3. Wessells H, et al. Urology. 2000;56:641-646.
4. Habbema L, et al. Int J Dermatol. 2017;56:975-980.
5. Wessells H, et al. Int J Impot Res. 2000;12 Suppl 4:S74-S79.