Comparison
PT-141 vs Melanotan II
The same parent molecule taken in two directions. One was refined until it stopped tanning you and got approved; the other kept every receptor it started with and never did.
PT-141 is a derivative of melanotan II. Removing an amide from the C-terminus cut most of its activity at MC1 — the receptor that darkens skin — and left the central MC4 activity behind. That single change is the whole difference between them.
It is also the difference between an approved medicine and a research chemical. PT-141 is licensed as bremelanotide for hypoactive sexual desire disorder in premenopausal women, with a phase 3 programme behind it and a dose cap in its labelling. Melanotan II has never been approved anywhere and has no completed human trial published.
They are routinely discussed as interchangeable because one came from the other. The pharmacology says otherwise: what melanotan II does to pigment is the part PT-141 was engineered to lose.
| Attribute | PT-141 | Melanotan II |
|---|---|---|
| Receptors | MC4 centrally, little MC1 | MC1, MC3, MC4 and MC5 — non-selective |
| Approval | Approved as bremelanotide (Vyleesi) | Approved nowhere, ever |
| Evidence | Phase 3 trials in the licensed indication | No completed human trial published |
| What it is taken for | Sexual desire | Tanning, with sexual effects as a side effect |
| Effect on pigment | Minimal — engineered out | Darkens skin, moles and nails |
| Dosing | 1.75 mg as needed, capped at 8 a month in the labelling | No established dose; commonly every other day |
| Nausea | Common in trials | Common, via the same central receptors |
| Priapism | Reported | Reported, sometimes requiring surgery |
| The melanoma question | Not raised — it barely touches MC1 | Case reports exist; causation is not established |
Things worth knowing
- The structural closeness is why people substitute one for the other, and the receptor selectivity is why that does not follow. PT-141 will not tan you, and melanotan II was never studied for the thing PT-141 is approved for.
- Melanotan II darkens existing moles as well as skin, which is the practical problem underneath the melanoma question: it makes the thing you are meant to watch for harder to watch. Dermatology bodies in several countries have issued warnings against it.
- PT-141's frequency cap — no more than once in 24 hours, eight times a month — is part of its approved labelling rather than a community convention. Melanotan II has no equivalent, because nothing has ever been approved to put one in.
- Neither is a tanning product with a safety record. One is a licensed medicine for something else entirely, and the other is unlicensed everywhere.
Full profile
PT-141
A melanocortin receptor agonist approved by the FDA for low sexual desire in premenopausal women. It acts on the brain rather than on blood flow.
Full profile
Melanotan II
A melanocortin agonist that darkens skin by stimulating melanin production. Carries the most serious dermatological concern of anything on this site.
Related
This page is educational. It describes what published research reports, not what you should do. Peptides discussed here are largely not approved for human use, and nothing on Bioalmanac is medical advice.