Melanotan II is an unlicensed and largely untested form of alpha-melanocyte-stimulating hormone, which causes pigmentation (tanning) of human skin. Melanotan II is a variant of melanotan I (afamelanotide), a drug used in the treatment of erythropoietic protoporphyria.

Melanotan II is not approved for the treatment of any medical conditions currently. It has been reported to cause a wide range of potentially serious side effects. Warnings against its use have been issued from the US, UK and several other countries.

How does melanotan II work?

Melanotan II non-selectively mimics the action of melanocortin peptides. These are natural hormones involved with pigmentation, energy homeostasis, sexual functioning, the immune system, inflammation, and the cardiovascular system. Much like melanotan I (afamelanotide), melanotan II stimulates the production of eumelanin, causing the skin to go darker (tanning).

Melanotan II is usually administered as an injection of liquid underneath the skin, commonly every second day. Trials have shown that the tanning effect can occur within 5 doses.

Side effects of melanotan II

Short term side effects after administration include:

• Facial flushing
• Reduced appetite, nausea and vomiting
• In males, spontaneous erections 1-5 hours after administration (priapism), associated with yawning and stretching complex

Long term, there is concern that melanotan II may increase the risk of:

• Melanoma – a potentially serious form of skin cancer
• Deepening of the colour of moles, new moles and atypical melanocytic naevi
• Melanonychia – brown to black discolouration of one or more nails
• Rhabdomyolysis – potentially fatal destruction of muscle cells
• Encephalopathy syndrome

There is also concern about possible side effects due to contamination or lack of sterility if melanotan II is prepared incorrectly or needles are shared.

Sexual dysfunction

During clinic trials for its use as a tanning agent, melanotan II was found to be a potent stimulator of male erections. A new drug based on melanotan II, bremelanotide, was developed to take advantage of this property. It has been noted across several studies to increase rigidity and duration of male erection, as well as male sexual desire. It has also been shown to increase female sexual desire in patients with sexual arousal disorder.

Drug interactions with melanotan II

No specific drug interactions have not been identified with melanotan II.

Safety measures

Melanotan II has not been fully tested, and due to its potential side effects it is not recommended that anybody use this drug.

No evidence exists for the use of melatonin II in pregnancy or breast feeding but it is recommended that it should be avoided.