What is melanotan?

In one line

Melanotan is a lab-made copy of the body's signal that darkens the skin, so it turns the skin brown without sunlight.

What is melanotan?
A drug injected to darken the skin
Among people who want darker skin before a competition, the name 'melanotan' comes up. Unlike tanning products that are sprayed or rubbed on, it is a drug that is injected. What exactly is it, and what does it do in the body?
In short
A copy of the body's skin-color signal
Melanotan is a lab-made drug that copies a signal substance in the body that darkens the skin. The skin turns brown even without sunlight. There are two kinds: melanotan-1 and melanotan-2.
What is melanin?
The pigment that colors skin and hair
The color of skin, hair and eyes comes from a brown-black pigment called 'melanin'. Melanin is made by 'melanocytes', cells in a deep layer of the skin. In the sun, these cells make more melanin and the skin tans.
Hormones and alpha-MSH
The body's signal that wakes up melanocytes
A hormone is a substance made in one part of the body that travels in the blood and carries a signal to another part. The hormone 'alpha-MSH (melanocyte-stimulating hormone)' tells melanocytes to make melanin. Melanotan was made as a copy of alpha-MSH.
What it does
It fits the melanocyte's 'lock'
Cells have spots where only certain substances fit, like a key in a lock. These are called 'receptors'. Melanotan attaches to a receptor on melanocytes (MC1R) and makes them produce more dark brown melanin. That is why the skin darkens without sunlight.
Melanotan-1
An approved drug for a rare disease
Melanotan-1 is a medicine called 'afamelanotide'. It is approved in Europe and the United States to treat a rare disease in which light makes the skin painful and swollen. It raises melanin in the skin so that less light gets into the skin.
Melanotan-2
Not approved for use in people
Melanotan-2 is not approved as a medicine for people. Even so, it is sold without approval and has spread among young people who go to gyms. Health Canada has reported seizing melanotan injections as unauthorized drugs.
Common side effects
Nausea and yawning
In early tests of melanotan-2 in people, nausea and yawning or stretching were common. In a test aimed at treating erection problems, about one in eight people had severe nausea at one of the doses. Nausea and headache were also common side effects of the approved melanotan-1.
Moles and melanoma
Moles darkened and new ones appeared
In people who used melanotan without approval, cases kept being reported of existing moles getting darker or changing shape, and of new moles appearing. Cases of 'melanoma' arising in a mole during or soon after use were also reported. Melanoma is a skin cancer that starts in melanocytes.
Muscles and kidneys
Cases of muscle breakdown and kidney damage
After unapproved melanotan use, cases of 'rhabdomyolysis' were reported. In this disease, muscle is badly damaged and its contents leak into the blood, and these contents harm the kidneys. A case in which blood flow to the kidney was blocked and part of the kidney died was also reported.
Common misconception
A 'tanning shot' only changes skin color?
No. Melanotan-2 does not pick only the skin's receptor; it also attaches to similar receptors in the brain and other places. In fact, in erection-problem tests, about 85% had an erection with no sexual stimulation. Painful erections that do not go down for hours were also reported as a serious side effect.
Summary
A copy of the skin-color signal
Melanotan is a drug made as a copy of alpha-MSH, the body's hormone that wakes up melanocytes, and it darkens the skin without sunlight. Melanotan-2 acts not only on the skin but also on the brain and other places. Related terms: melanin, competition tanning, melanoma.