Comparison
PT-141 vs afamelanotide
Both are melanocortin agonists derived from the same parent peptide, and they are used for entirely different things: one for sexual desire, the other for light tolerance in a rare blood disorder.
Both descend from melanotan II, and which melanocortin receptor each favours decides what it does.
PT-141, bremelanotide, acts centrally through MC4 and is approved for hypoactive sexual desire disorder in premenopausal women. Afamelanotide acts on MC1 in the skin, stimulating eumelanin, and is approved to reduce phototoxicity in erythropoietic protoporphyria.
The overlap is real enough to cause confusion — receptor selectivity is a preference rather than a switch, so PT-141 can darken skin and afamelanotide has been reported to affect libido.
| Attribute | PT-141 | Afamelanotide |
|---|---|---|
| Main receptor | MC4, centrally | MC1, in the skin |
| Evidence level | Approved for another indication | Approved |
| Approved for | Hypoactive sexual desire disorder | Erythropoietic protoporphyria |
| Route | Subcutaneous or nasal | Subcutaneous implant |
| Dosing frequency | As needed, up to eight times a month | One implant every two months |
| Half-life | About 2.7 hours | About a day for the peptide |
| Effect on skin colour | Possible, unintended | The intended effect |
Things worth knowing
- Receptor selectivity is relative. Neither is clean, which is why the effect each is not being used for still turns up as a side effect.
- The dosing forms are not comparable. One is taken before an occasion and clears in hours; the other is an implant releasing over months, and stopping it is not a matter of skipping a dose.
- Both are approved for narrow indications in specific populations. Cosmetic tanning is not one of them, and it is the use these are most often bought for.
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
Afamelanotide
The approved member of the melanotan family. Same idea as melanotan II, taken through a full regulatory process, and the contrast between them is instructive.
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.