Inside the Viral Tanning Peptide That Accidentally Created Vyleesi’s FDA-Approved Low Sex Drive Drug
Unverified “sunless tanning” injections are exploding across social media, but their real scientific legacy isn’t a dark complexion. Here is how Melanotan’s unexpected side effect yielded a first-of-its-kind treatment for female libido.
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If you’ve scrolled #wellnesstok recently, you’ve probably seen Melanotan promoted as an injectable shortcut to a sun-kissed tan. No UV exposure required. But what most videos don’t mention is that the compound never received FDA approval or what researchers found buried in those early trial results.
On this week’s episode of the Live + Well podcast, Beverly Hills physician Dr. Daniel Ghiyam unpacks the surprising science behind Melanotan, why regulators rejected it, and how researchers ultimately transformed one of its unexpected side effects into the FDA-approved women’s health drug Vyleesi.
To understand how that happened, it helps to first understand how tanning actually works.
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How Melanotan Works and Why Regulators Rejected It
Tanning is actually a defense mechanism. When ultraviolet radiation hits your skin at levels the body perceives as harmful, it activates the melanocortin system, a signaling pathway that instructs melanocytes, the cells responsible for pigment production, to increase melanin. The resulting darkening of the skin helps absorb and deflect UV radiation before it can damage deeper tissue. Melanotan was designed to activate that same pathway without any sun exposure.
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“Think about when the sun hits your skin,” says Dr. Daniel Ghiyam, who specializes in anti-aging medicine and peptide therapy at Med Pod LA. “Your brain is says, ‘this is dangerous for us. So it releases a peptide to tan it, to protect itself.” Melanotan was developed to mimic that same natural peptide, triggering the body’s tanning response without requiring UV exposure. Because that concept, scientifically, made sense, the compound advanced into human clinical trials.
Driven by GLP-1 shortages and FDA compounding restrictions, a multi-billion-dollar gray market for injectable peptides exploded online. The four words printed on those vials should stop you cold.
And participants did, in fact, develop darker skin…but researchers also uncovered a pattern of side effects that ultimately stopped the drug’s path to approval. According to studies, severe nausea and headaches were common while taking Melanotan, and some participants experienced uncontrolled darkening of existing moles and pigmentation. Those findings raised concerns about skin cancer risks that regulators were unwilling to overlook.
From Tanning Shortcut to Libido Drug: The Science Behind Vyleesi
And so while Melanotan never became a prescription drug, researchers kept looking at the data anyway, because something was showing up across trial participants that nobody had designed the study to find. A marked, reproducible increase in sexual arousal. Scientists then traced the pathway responsible and found it was entirely separate from the tanning mechanism, rooted in melanocortin receptor activity in the hypothalamus (the brain region involved in regulating motivation and desire) rather than in the skin. The new compound they developed targeted only this brain pathway, with the pigmentation mechanism removed.
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“A different peptide, PT-141, that did get FDA approval, and then named Vyleesi, came from that,” Ghiyam explains. “They took that one, and it got FDA approval for premenopausal women with sexual desire disorder.”
In 2019, it received FDA approval for the treatment of hypoactive sexual desire disorder (HSDD), a condition in which a persistently low interest in sex becomes distressing to the individual and isn’t simply the result of aging, relationship difficulties, or another health condition. HSDD is estimated to affect about 10% of women in the United States, according to a 2022 review in CNS Spectrums, and Vyleesi is one of only two FDA-approved therapies specifically indicated for female sexual desire.
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Vyleesi is self-administered as a shot delivered just under the skin, 30 to 60 minutes before anticipated sexual activity. Acting on the brain rather than reproductive tissue, it leaves hormone levels untouched. Some nausea can still occur in a portion of users, a faint echo of its Melanotan origins, but the pigmentation risks have been engineered out. The 2019 approval, detailed in a 2020 drug review in the Annals of Pharmacotherapy, represented one of the first times the FDA had formally addressed female sexual desire as a clinical target.
The Dangers of TikTok’s Gray-Market Melanotan Trend
Despite all of that history, vials of Melanotan I and Melanotan II continue to circulate on gray-market websites. “A lot of people just ChatGPT this stuff, ordering it on some website that they don’t know where it’s coming from and then just injecting themselves,” says Ghiyam. The quality of what arrives is unknowable.
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“I know somebody who tests some of these batches,” he notes, “and he says one out of ten he sees is not right. It’s not even anything close to it.” Many of the sellers have no verifiable physical presence. “If you go look at the address on Google Earth, no such building exists,” Ghiyam explains. “And some even require payment in cryptocurrency.” Some vials, he explains, often carry a label that describes them as not for human use, research use only.
Another concern, Ghiyam explains, is that peptides are delicate compounds. Heat, sunlight, and improper handling during shipping can break them down, meaning the product that arrives at your door may not be the same as what was originally manufactured (or what the label claims you’re getting).
Once thought to be a condition affecting only older men, erectile dysfunction is increasingly impacting men in their 20s and 30s. A complex mix of hormonal imbalances, chronic stress, and poor sleep are signs ED is less about performance.
And the safety concerns that kept Melanotan from earning FDA approval haven’t disappeared just because it’s being sold online. According to Ghiyam, researchers were particularly concerned about uncontrolled darkening of existing moles and other pigmentation changes, which contributed to the decision not to approve the drug. Ghiyam says Melanotan could have a future if there were more studies, but for now, people who buy Melanotan online now are essentially using a compound that researchers left behind and should be wary.
Listen to the full episode of the Live & Well podcast on Spotify and Apple Podcasts.
