Three melanocortin-pathway compounds get sold for libido: PT-141, kisspeptin and melanotan-2. Only one has been through full phase 3 trials and an approval. The other two carry human data, but of a very different kind, and one of them comes with a safety record serious enough that it shapes the ranking as much as its efficacy data does. This guide ranks all three by what was actually tested, and where each stands with regulators.
Summary
| Compound | Best evidence | Stage |
|---|---|---|
| PT-141 (bremelanotide) Stocked locally | RECONNECT phase 3 trials, 1,267 premenopausal women | FDA-approved 2019 (Vyleesi) |
| Kisspeptin | Randomised, placebo-controlled single-dose crossover trials in small groups of men and women | Human pilot studies; not approved |
| Melanotan-2 | A small 1990s placebo-controlled crossover trial in men with erectile dysfunction, plus a large dermatology case-report record | Never approved; regulator warnings |
PT-141: the only approved medicine in this group
PT-141 is the development code for bremelanotide, a melanocortin receptor agonist that activates MC4R and MC3R in the brain rather than acting on blood vessels the way erectile dysfunction drugs do. The US FDA approved it in June 2019 as Vyleesi, a 1.75 mg autoinjector, based on the two identical RECONNECT phase 3 trials: 1,267 premenopausal women with acquired, generalized hypoactive sexual desire disorder (HSDD) were randomised to bremelanotide or placebo, injected as needed, over 24 weeks. Both trials found statistically significant increases in desire scores and reductions in distress about low desire, though the label is candid that the exact mechanism behind that improvement in women "is unknown". The trade-off is a demanding side-effect profile: 40% nausea versus 1.3% on placebo, 20.3% flushing, and a brief rise in blood pressure after each dose. PT-141 was also studied in men with erectile dysfunction decades earlier, but that work never reached an approval, and the current label states it is not indicated for men.
Kisspeptin: single-dose human trials in both sexes, no treatment course tested
Kisspeptin is the natural signal that switches on the reproductive axis, and a research group at Imperial College London has run the closest thing to head-to-head sex-specific trials in this guide. A 2022 randomised, double-blind crossover trial gave 32 premenopausal women with HSDD a single 75-minute infusion of kisspeptin-54, and it changed brain activity in response to erotic videos and male faces compared with placebo. A matching 2023 trial in 32 men with HSDD found greater activation of sexual brain networks and penile rigidity reported up to 56% higher than on placebo during erotic videos. Both trials reported kisspeptin as well tolerated with no side effects, but each was a single infusion in a scanner, not a repeated-dose trial, and none has measured sexual activity outside the research setting. Kisspeptin is not approved anywhere, and the US FDA added kisspeptin-10 to its list of compounding substances that may raise safety concerns in 2023.
Melanotan-2: real early trial data, and a safety record that changed the field
Melanotan-2 activates the same melanocortin receptors as PT-141, plus MC1R, the pigment receptor, which is what makes it tan skin as well as raise arousal. Its human data is older and thinner: a 1996 pilot study tested it as a tanning agent, and a 1998 double-blind, placebo-controlled crossover trial found it initiated erections in men with psychogenic erectile dysfunction. Neither trial was designed around sexual desire specifically, and neither has been repeated or extended since the 1990s.
What sets melanotan-2 apart is what happened after those trials: since 2009, dermatology journals have published a steady series of case reports describing new and changing moles, and melanoma diagnosed in users, including a 20-year-old woman who had used it for three to four weeks alongside sunbed use before her melanoma was found. The UK's MHRA calls the "tan jab" an unlicensed medicine that may not be safe, and Australia's TGA issued an urgent warning in August 2026 after seized products were found to contain far more of the peptide than labelled. Melanotan-2 was never developed into an approved medicine; PT-141 exists specifically because researchers tried to keep the arousal effect while dropping the receptor activity behind the mole and pigment concerns.
Safety notes
PT-141's most common problems, nausea and a brief blood pressure rise, are managed within a supervised, dose-limited regimen on an approved label. Kisspeptin's safety record is limited to short, well-tolerated single sessions, so anything about longer use is unknown. Melanotan-2 carries the clearest documented risk of the three: anyone who has used it and notices a new, changing or darkening mole should see a dermatologist rather than wait.
Why the three compounds are not interchangeable
It is worth being precise about what each one is actually built to do, since all three get grouped under "libido peptides" in the same online listings. PT-141 targets desire through a brain receptor and has a defined, approved dose and monitoring plan behind it. Kisspeptin targets the reproductive axis itself, and its brain-imaging effects were a secondary finding in studies designed around hormone physiology, not a purpose-built desire treatment. Melanotan-2 was designed as a tanning agent, and its arousal effect was a side finding researchers later tried to isolate and improve on, which is the project that produced PT-141. None of that history changes what belongs with a physician: any of the three, if considered at all, is a conversation for a licensed Philippine physician rather than a self-directed purchase.
Status in the Philippines
No bremelanotide, kisspeptin or melanotan-2 product is registered with FDA Philippines, so none can be sold locally as a medicine, and none is a controlled substance under RA 9165. Where they circulate, it is only through research-peptide suppliers. As an approved medicine abroad, PT-141 prescribing belongs with a licensed Philippine physician, who can also check blood pressure and cardiovascular history before use.
