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PT-141 vs Melanotan II

Last updated: October 3, 2026 · 5 min read · By the Grey Peptides Editorial Board

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Grey Peptides
Grey Peptides Editorial Board
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Key takeaways
  • PT-141 and melanotan II are related synthetic melanocortin agonists that act on overlapping receptors.
  • PT-141 is FDA-approved as Vyleesi for low sexual desire in premenopausal women, after trials in 1,267 women.
  • Melanotan II is unapproved; its human evidence is studies of 3 and 20 men, plus case reports of serious harm.
  • Each darkens skin and affects sexual function to some degree, which is why combining them doubles up.

Side by side

PT-141 High and melanotan II Low come from the same chemistry and are often confused 1. The table is read from our encyclopedia entries.

FieldPT-141Melanotan II
Encyclopedia entryPT-141 Full entryMelanotan II Full entry
Molecule classPeptidePeptide
CategorySexual HealthSexual Health
FDA statusFDA ApprovedResearch Chemical
Approved elsewhereNone recordedNone recorded
Evidence gradeHighLow
Half-life≈ 2.7 hoursNot measured in humans
FormulaC50H68N14O10C50H69N15O9
Molecular weight1,025.2 g/mol1,024.2 g/mol
WADA 2026Not on the 2026 ListProhibited (S0 catch-all)
WADA 2027Not on the 2027 ListProhibited (S0 catch-all)
In one lineAn FDA-approved melanocortin agonist for acquired, generalized hypoactive sexual desire disorder in premenopausal women.An unapproved melanocortin agonist sold as a tanning and libido injection, with small 1990s trials and case reports of changing moles, melanoma, priapism and kidney injury.
MechanismNon-selective melanocortin receptor agonist. The label ranks its potency MC1R > MC4R > MC3R > MC5R > MC2R, names MC1R and MC4R as most relevant at the approved dose, and calls the mechanism by which it improves desire unknown. In female rats it increased solicitation behaviour through the medial preoptic area, possibly by releasing dopamine. Each dose transiently raises blood pressure and lowers heart rate; MC1R activity is the likely source of focal hyperpigmentation.Non-selective agonist at MC1R (melanocyte stimulation → melanin production and tanning), MC3R and MC4R (central — appetite suppression and sexual arousal via hypothalamic pathways), and MC5R (sebaceous gland stimulation). The central MC4R agonism underlies both the increased libido/spontaneous erections reported by users and the adverse effects (nausea, yawning, flushing). MC1R agonism drives eumelanin synthesis but also stimulates melanocyte proliferation — the likely mechanism behind the mole changes and atypical nevi reported in case series.
Sources in the entry1920
Study cards1614
Dosage pageDosage pageDosage page

Same family, different fates

Both are synthetic agonists of melanocortin receptors, the family behind skin pigment, appetite and sexual function. Melanotan II is unselective across that family (laboratory study) 2; PT-141, bremelanotide, was developed as a self-administered, on-demand agonist with high affinity for the MC4 receptor (drug profile) 3. That difference in focus, and a full clinical programme, is why one became an approved medicine and the other did not.

PT-141: an approved drug with modest effects

FDA approved bremelanotide as Vyleesi for premenopausal women with acquired, generalised hypoactive sexual desire disorder; the label excludes postmenopausal women, men and use to enhance performance 4. In two trials of 1,267 women, desire scores rose and distress fell slightly more than on placebo (randomised trials) 5. A 2022 analysis of the programme reported nausea in 40.0% against 1.3% on placebo, flushing in 20.3% and headache in 11.3% (review of trials) 6. Ambulatory monitoring in 397 women found small blood pressure rises after dosing (randomised trial) 7. Our PT-141 guide covers the trials in detail.

It was also tested in men: in 342 married men whose erectile dysfunction had not responded to sildenafil, a nasal spray produced a positive response in about a third (randomised trial) 8. That use was never approved, and men remain outside the label 4. Anyone using PT-141 off-label is relying on trials that did not lead to approval for that group.

Melanotan II: tiny studies and case reports

Melanotan II's human evidence is very small. In three healthy men given injections on alternate days for two weeks, two developed increased pigmentation (human study) 9. Crossover studies in 20 men with erectile dysfunction reported erections without stimulation in 17 of 20, with nausea and yawning common (small human studies) 10. A 2020 case report attributed a kidney infarction to it and reviewed earlier reports of rhabdomyolysis and kidney failure (case reports) 11. Vials sold online as 10 mg contained 4.32 to 8.84 mg, some with unknown impurities (laboratory analysis) 12. Every one of these findings comes from small studies or individual cases; no trial has measured how common its harms are, which is a reason for more caution, not less.

Where they overlap

Each does some of what the other is sold for. Melanotan II produced sexual effects in its small studies 10, and PT-141's label warns of focal skin darkening, which is why it caps monthly use 4. Both cause nausea 6 10. That overlap is why taking them together, a common online stack, stacks the same effects rather than combining a tan with a libido boost; our melanotan II and PT-141 page covers that combination.

Questions to ask before choosing either

  • Am I a premenopausal woman with diagnosed low desire, for whom the approved product exists?
  • Do I have high blood pressure or heart disease? The Vyleesi label warns about blood pressure rises.
  • Is the product an approved medicine or an online vial, which for melanotan II has been found under-filled?
  • Am I subject to anti-doping rules?

How the differences add up (as of October 3, 2026)

PT-141 has a full trial programme, an FDA approval for one narrow use, modest benefits and well-described side effects. Melanotan II has studies of three and twenty men, serious case reports and a quality problem in what is sold. For sport, PT-141 is not on the WADA list; melanotan II falls under S0 by our reading 1. Doses on this page are those in our entries' sources, not recommendations.

Frequently asked questions

What is the difference between PT-141 and melanotan II?

Both are synthetic melanocortin agonists. PT-141 is FDA-approved as Vyleesi for low sexual desire in premenopausal women; melanotan II is unapproved and sold online mainly for tanning.

Does melanotan II increase libido?

In small studies in men it produced erections and more desire, alongside nausea. It is not approved for any use.

Does PT-141 cause tanning?

Its label warns of focal skin darkening, which is why monthly use is capped.

Sources

  1. Grey Peptides dataset records for PT-141 (Vyleesi, approved) and melanotan II (not approved; WADA S0 inferred), studied doses as sourced on each entry; read October 3, 2026.
  2. Tomassi, S., et al. (2022). CLIPSing Melanotan-II to Discover Multiple Functionally Selective hMCR Agonists. J Med Chem, 65(5), 4007-4017. PMID: 35188390
  3. Dhillon, S., et al. (2019). Bremelanotide: First Approval. Drugs, 79(14), 1599-1606. PMID: 31429064
  4. VYLEESI (bremelanotide injection) US prescribing information: Indications and Usage with Limitations of Use, Warnings and Precautions. DailyMed version 1, effective November 13, 2025; read October 1, 2026.
  5. Kingsberg, S. A., et al. (2019). Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials. Obstet Gynecol, 134(5), 899-908. PMID: 31599840
  6. Clayton, A. H., et al. (2022). Safety Profile of Bremelanotide Across the Clinical Development Program. J Womens Health (Larchmt), 31(2), 171-182. PMID: 35147466
  7. White, W. B., et al. (2017). Usefulness of ambulatory blood pressure monitoring to assess the melanocortin receptor agonist bremelanotide. J Hypertens, 35(4), 761-768. PMID: 27977473
  8. Safarinejad, M. R., et al. (2008). Salvage of sildenafil failures with bremelanotide: a randomized, double-blind, placebo controlled study. J Urol, 179(3), 1066-71. PMID: 18206919
  9. Dorr, R. T., et al. (1996). Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sci, 58(20), 1777-84. PMID: 8637402
  10. Wessells, H., et al. (2000). Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II. Int J Impot Res, 12 Suppl 4, S74-9. PMID: 11035391
  11. Peters, B., et al. (2020). Melanotan II: a possible cause of renal infarction: review of the literature and case report. CEN Case Rep, 9(2), 159-161. PMID: 31953620
  12. Breindahl, T., et al. (2015). Identification and characterization by LC-UV-MS/MS of melanotan II skin-tanning products sold illegally on the Internet. Drug Test Anal, 7(2), 164-72. PMID: 24771717

Educational information, not medical advice. Each dose in this guide names its source, an approved label or a published study. None is a recommendation for you. An unapproved compound has no established safe or effective human dose, and products sold for “research use only” are not made or tested for people. Talk to a doctor before acting on anything on this site, including before you start, stop or change any medicine or dose.

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