Melanotan II (MT-2) common uses, half-life, side effects and more

Melanotan II is a synthetic peptide that makes skin produce pigment without sun exposure. It was developed in the 1980s as a sunless tanning agent and was never approved by any regulator. People buy it as an unlicensed powder and inject it under the skin. Nasal sprays are also sold. It suppresses appetite and causes spontaneous erections as well as tanning because it activates receptors in the brain and not only in skin. It is the more widely used of the two tanning peptides.

• Darker skin with less sun exposure
• Appetite suppression
• Erections and increased sexual desire
• Tanning ahead of a holiday or a competition

Daily or every other day in documented cases

Documented use is 250 to 1,000 mcg injected under the skin daily or every other day. One recorded case escalated from 250 to 1,000 mcg over a week. Another ran 400 mcg every other day for two months. The only supervised dosing was about 0.025 mg per kg a day. That works out near 2,000 mcg for an average adult. No loading and maintenance schedule has been established despite how often one is quoted. The milligram figure on a vial cannot be trusted. Vials labeled 10 mg have been measured holding between 4.3 and 8.8 mg.

No human study has ever measured how long Melanotan II lasts in the blood. Any half-life figure quoted for it is borrowed from a different molecule. What has been measured is the effect rather than the drug. Tanning peaked about a week after dosing ended in the one trial that measured it. Erections came and went for one to five hours after a dose.

• Nausea after most doses with severe nausea in about one in eight at the studied dose
• Spontaneous erections in most men without sexual stimulation lasting one to five hours
• Yawning and stretching that arrive together with the erections
• Loss of appetite
• Darkening of existing moles and freckles
• Drowsiness at higher doses

Melanotan II activates all of the melanocortin receptors rather than only the pigment one. Switching on the pigment receptor in skin drives production of the darker pigment without any sun. Switching on the appetite and arousal receptor in the brain drives the loss of appetite and the spontaneous erections. Those brain effects are inferred from what human trials observed rather than from measuring the drug in the brain. Yawning and stretching appear alongside the erections as a linked complex. The approved drug for low sexual desire in women differs from Melanotan II by a single chemical group at one end of the molecule. Pigment lasts far longer than the drug does because color fades with skin turnover rather than with drug clearance.

Human evidence is thin. Only three small controlled trials exist and they enrolled 23 people in total. Those trials measured tanning and erections over days rather than long-term safety. No trial has run since 2000 and none tested the product people buy. Most of what is known about harm comes from single case reports and from surveys of users. Two recent case reports document the doses people actually inject. The molecule did lead to an approved medicine for low sexual desire in women.

• Existing moles darken and new moles can appear within a day of a single injection
• The pigment changes make moles harder to read on a skin check so it undermines the surveillance used to catch melanoma early
• Four melanoma cases have been reported in melanotan users though no study has shown that it causes melanoma
• An erection lasting more than four hours is a medical emergency and one reported case needed surgery to resolve it
• Overdose has caused a racing heart, sweating, tremor, and muscle breakdown that needed intensive care
• Avoid it in pregnancy and breastfeeding since nobody has studied it