Melanotan II: What It Is, Where to Get It Prescribed, and What It Costs

Melanotan II is a synthetic analogue of alpha-melanocyte-stimulating hormone, or alpha-MSH — the small peptide your skin releases after sun exposure to tell pigment cells called melanocytes to make more melanin. It keeps the seven amino acids of alpha-MSH that do the receptor binding, swaps in a few modified residues, and closes the chain into a ring with a lactam bridge. The published sequence is Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2.

That ring is the point. Natural alpha-MSH is broken down within minutes; the cyclic structure makes Melanotan II far more resistant to enzymes and considerably more potent, which is why the 1996 pilot study called it "superpotent" and why it produced visible pigmentation after a handful of low doses.

Melanotan II was designed in the 1980s at the University of Arizona by the Hruby and Hadley laboratories, which had already produced Melanotan I, a linear analogue that became afamelanotide, the active ingredient in an approved implant for a rare light-sensitivity disorder. Melanotan II was the second-generation, cyclic compound. A metabolite of it was later developed as bremelanotide, better known as PT-141, approved under a brand name for low sexual desire in premenopausal women. Three names that get confused; three different molecules with a shared ancestry.

It is not a sunscreen and does not block ultraviolet light; the research does not describe it preventing sunburn or skin cancer. It is not selective: unlike afamelanotide, which is relatively focused on the skin's MC1 receptor, it activates several melanocortin receptors at once, which is why it also affects erections, sexual desire and appetite. And it is not a hormone in the endocrine sense: it does not bind androgen or oestrogen receptors and does not suppress your own hormone production.

The skin effect runs through the MC1 receptor on melanocytes. When alpha-MSH or Melanotan II binds MC1R, the cell raises cyclic AMP, switches on tyrosinase and shifts production toward eumelanin, the brown-black pigment that gives a tan its colour, rather than the red-yellow pheomelanin. This is the pathway ultraviolet light uses; Melanotan II turns it on without the ultraviolet step. In the 1996 pilot study, pigmentation was measured in the face, upper body and buttocks — areas the volunteers had not been exposing — which fits a systemic signal rather than a local one.

The MC4 receptor in the hypothalamus and spinal cord is the pathway behind the erectile effect. Animal work established that central melanocortin signalling initiates erections independently of the local nitric-oxide mechanism that sildenafil-type drugs act on, and the human crossover studies confirmed it in men: erections began without sexual stimulation and were rigid enough to register on a RigiScan monitor. This is a centrally initiated erection, not a blood-flow drug.

The same receptor family is implicated in sexual motivation, which is separate from the mechanics of an erection. In the human studies men reported higher sexual desire after Melanotan II than after placebo, and that observation is what led to bremelanotide being developed as a desire drug rather than an erection drug.

Melanocortin signalling in the hypothalamus is one of the body's main satiety systems. Animal studies describe Melanotan II reducing food intake, and "decreased appetite" appeared on the side-effect questionnaires in the human studies. It is a documented effect, not a marketed one, and not what the compound is prescribed for.

Every human study noted a "stretching and yawning complex" that tends to precede the erections. It is a recognised melanocortin effect seen in animals decades earlier: transient, dose-related, and worth knowing about in advance because it is otherwise alarming.

The direct human evidence is the pilot phase I study published in Life Sciences in 1996. Three healthy male volunteers received subcutaneous Melanotan II or saline on alternating weekdays for two weeks, with dose escalation. Two of the three showed increased pigmentation in the face, upper body and buttocks, measured by reflectance and by eye, a week after dosing ended; the authors concluded that Melanotan II has tanning activity in humans after only five low doses. That is the whole formal pigmentation dataset: a three-person, single-blind pilot that showed the effect clearly but was not designed to measure how much, how evenly, or how long.

This is where the human data is stronger. The Journal of Urology published a double-blind, placebo-controlled crossover study in 1998 in ten men with psychogenic erectile dysfunction: erections developed in eight of ten on Melanotan II, with 38 minutes of tip rigidity above 80 percent versus 3 minutes on placebo. A companion study in Urology in 2000 repeated the design in ten men with organic erectile dysfunction and reported erections after 12 of 19 active injections versus 1 of 21 placebo. A pooled review in the International Journal of Impotence Research in 2000 reported erections in 17 of 20 men and increased sexual desire after 68 percent of active doses versus 19 percent of placebo.

These are small, single-dose studies. But they are randomised, placebo-controlled and objectively measured, and they establish that Melanotan II initiates erections in men. The desire finding was a secondary, questionnaire-based measure; that signal was pursued with bremelanotide rather than Melanotan II itself.

Reduced appetite was recorded as a side effect in the human studies and is described in animal work as a melanocortin effect. No human trial has studied Melanotan II for appetite or weight, and this page does not describe it as a weight tool.

Precisely: one three-person pilot pigmentation study, two ten-person randomised placebo-controlled crossover studies in erectile dysfunction, and a pooled review, all from one research group in the 1990s. There are no large randomised controlled trials of Melanotan II in humans, and there are no controlled trials of repeated dosing over weeks or months, which is the way it is actually prescribed. Beyond that the human literature is case reports and clinical experience. That is a more solid human footing than most compounded peptides have, and a much thinner one than an approved drug.

• It does not establish how dark a tan a given person will get, or how evenly. The pilot study measured a change; it did not characterise it.
• It does not establish how long pigmentation persists after stopping.
• It does not establish long-term safety over repeated courses. Nobody has followed a cohort for years.
• It does not establish whether it changes melanoma risk in either direction. There are case reports of moles changing and of melanoma diagnosed during or after use; a 2017 review in the International Journal of Dermatology concluded that conclusive evidence of a causal link is lacking but that the reports warrant caution.
• It does not establish efficacy for any condition as an approved treatment. Melanotan II is not approved for anything.

The first week is mostly about side effects rather than colour. Nausea, facial flushing, warmth and the stretching-and-yawning sensation are what people notice, usually within an hour or two of an injection and settling the same day. In men, spontaneous erections in the hours after a dose are expected. Prescribers describe these effects as most pronounced at the start and fading with repeated dosing; if nausea is a problem, evening injection is a common adjustment, but that is your physician's call.

Pigmentation, where it occurs, tends to show first in areas that already carry pigment: moles, freckles, the face, the upper body. Moles darkening is expected and is why your skin is examined before you start — a darker mole is not itself a warning sign, but one that changes shape, border or texture is, and you need a baseline to tell the difference. Modest sun exposure is usually described as part of the picture; nothing here should be read as encouraging sunbeds.

There is no withdrawal described. Pigment fades as skin cells turn over, so for most people the tan recedes over several weeks once dosing stops. Whether a further vial is prescribed is decided at refill review, not automatically.

Anyone on Melanotan II should check their skin regularly and have any new or changing pigmented lesion looked at promptly. It is the single most important practical point on this page.

The directions are written in millilitres and insulin-syringe units because that is what you can read off the barrel. 0.25 mL is 25 units on a U-100 syringe. You are not calculating anything — the number is printed on your medication, and your physician sets it.

Subcutaneous means into the fat layer, not the muscle. Abdomen and thigh are the usual sites, rotated. Because the melanocortin signal is systemic, where you inject does not decide where you tan.

The reviewed directions are five days a week with the weekend off, as the human research used. It gives a predictable break from the side effects while keeping the pigment signal going. 20 doses at five per week is four weeks, which is why refills run on a 28-day cycle. One vial per fill, always — not a stockpile.

Refrigerated, and it ships that way in insulated packaging with ice packs. A fresh sterile syringe every time; beyond-use dating runs from first puncture and is on the label.

PT-141 is bremelanotide, a metabolite of Melanotan II. The two act on the same receptors, but PT-141 was developed specifically for sexual function and its pigmentation effect is comparatively minor. If tanning is not the goal, PT-141 is the more targeted choice; if it is, PT-141 will not deliver it.

Melanotan I is afamelanotide, a linear analogue relatively selective for the skin's MC1 receptor, approved as an implant for erythropoietic protoporphyria, a rare disorder of severe light sensitivity. It is not a compounded product. Melanotan II is the cyclic, non-selective sibling: more potent, and carrying the erection, desire and appetite effects that Melanotan I largely does not.

Ultraviolet tanning damages DNA in the process of producing pigment, which is where its skin-cancer risk comes from. Melanotan II produces eumelanin without the ultraviolet step, but it stimulates melanocytes directly, and whether that carries its own long-term risk is the unresolved question in the case-report literature. They are different risks, not the absence of one. A darker tone from Melanotan II is not enough protection to skip sunscreen.