Comparison
Melanotan II vs PT-141
Both are melanocortins, so the meaningful differences are in kinetics, evidence and regulatory status.
On published evidence alone, PT-141 is the better documented of the two (regulator approved). That is a statement about the state of the literature, not a recommendation.
| Melanotan II | PT-141 | |
|---|---|---|
| Class | Melanocortins | Melanocortins |
| Evidence | Preliminary human | Regulator approved |
| Human trials | ~6 | ~20 |
| Half-life | ~1-2 hours | ~2.7 hours |
| Reported range | 250 mcg - 1 mg | 1-2 mg |
| Frequency | Daily loading then 2-3x weekly maintenance | As needed, at most once per 24 hours and 8 doses per month |
| Routes | Subcutaneous | Subcutaneous, Intranasal |
| FDA approved | No | Yes |
| Research use only | Yes | No |
| Banned in sport | No | No |
| Studied for | Tanning, Appetite suppression, Erectile function | Hypoactive sexual desire disorder in premenopausal women, Erectile dysfunction research |
| Reported side effects | Nausea, Facial flushing, Spontaneous erections, Darkening of moles, Appetite loss, Lethargy | Nausea, Flushing, Injection-site reactions, Headache, Transient blood pressure increase |
Melanotan II
Melanotan II is a cyclic lactam analog of alpha-melanocyte-stimulating hormone that activates melanocortin receptors non-selectively, including MC1R, MC3R and MC4R. MC1R activation drives melanogenesis and tanning; MC4R activation produces the appetite suppression and the erectile effects that led to the development of the selective derivative bremelanotide. Non-selectivity is precisely the problem: users cannot obtain one effect without the others, and health agencies in several countries have issued warnings about unregulated supply and about melanoma risk from darkening existing naevi.
PT-141
Bremelanotide is a metabolite of melanotan II in which the C-terminal amide is replaced by a hydroxyl group, shifting selectivity toward melanocortin-4 receptors and away from MC1R. It acts on hypothalamic pathways governing sexual desire and arousal, a mechanism fundamentally different from PDE5 inhibitors, which act on penile vasculature. That distinction means it can work where sildenafil does not, and also that it does not require a vascular response to be effective.
Melanotan II vs PT-141: common questions
What is the difference between Melanotan II and PT-141?
Both are melanocortins. Melanotan II: A non-selective melanocortin agonist that causes tanning, appetite suppression and erections. Subject of repeated regulatory warnings. PT-141: A melanocortin-4 selective agonist approved for hypoactive sexual desire disorder, acting centrally rather than vascularly.
Which has stronger evidence, Melanotan II or PT-141?
PT-141 has the stronger evidence base (regulator approved, about 20 human studies) compared with Melanotan II (preliminary human).
Are Melanotan II and PT-141 FDA approved?
Only PT-141 is FDA approved (Acquired, generalised hypoactive sexual desire disorder in premenopausal women (Vyleesi)). Melanotan II is not approved for any indication.
References
Regulatory and primary sources
- PubChem compound record (CID 92432) ↗ · structure, identifiers, synonyms
- FDA: Unapproved drugs and "research use only" products ↗ · regulatory status of non-approved products
- CAS Registry Number 121062-08-6 ↗ · chemical identity
- PubChem compound record (CID 9941379) ↗ · structure, identifiers, synonyms
- DailyMed: FDA-approved labeling for PT-141 ↗ · indications, dosing, warnings as approved
- FDA Drugs@FDA database ↗ · approval history
- CAS Registry Number 189691-06-3 ↗ · chemical identity
Published literature
- Falsification of biotechnology drugs: current dangers and/or future disasters?.J Pharm Biomed Anal 2018.PubMed 30165334 · doi:10.1016/j.jpba.2018.08.037
- Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization.Peptides 2006.PubMed 16412534 · doi:10.1016/j.peptides.2005.01.029
- Sympathetic and sensory innervation of brown adipose tissue.Int J Obes (Lond) 2010.PubMed 20935665 · doi:10.1038/ijo.2010.182
- Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II.Int J Impot Res 2000.PubMed 11035391 · doi:10.1038/sj.ijir.3900582
- Melanotan II: a possible cause of renal infarction: review of the literature and case report.CEN Case Rep 2020.PubMed 31953620 · doi:10.1007/s13730-020-00447-z
- Central nervous system agents in the treatment of erectile dysfunction: how do they work?.Curr Urol Rep 2001.PubMed 12084236 · doi:10.1007/s11934-001-0044-6
- Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study.Life Sci 1996.PubMed 8637402 · doi:10.1016/0024-3205(96)00160-9
- Discovery that a melanocortin regulates sexual functions in male and female humans.Peptides 2005.PubMed 15996790 · doi:10.1016/j.peptides.2005.01.023
- PT-141 Palatin.Curr Opin Investig Drugs 2004.PubMed 15134289
- Bremelanotide: First Approval.Drugs 2019.PubMed 31429064 · doi:10.1007/s40265-019-01187-w
- Hypoactive Sexual Desire Disorder in Women: Physiology, Assessment, Diagnosis, and Treatment.J Midwifery Womens Health 2021.PubMed 34510696 · doi:10.1111/jmwh.13283
- Targeting the central melanocortin system for the treatment of metabolic disorders.Nat Rev Endocrinol 2023.PubMed 37365323 · doi:10.1038/s41574-023-00855-y
- Pharmacotherapy for Sexual Dysfunction in Women.Curr Psychiatry Rep 2022.PubMed 35102537 · doi:10.1007/s11920-022-01322-7
- Pharmacologic therapeutic options for sexual dysfunction.Curr Opin Obstet Gynecol 2022.PubMed 36036468 · doi:10.1097/GCO.0000000000000821
- Medical Treatment of Female Sexual Dysfunction.Urol Clin North Am 2022.PubMed 35428435 · doi:10.1016/j.ucl.2022.02.001
- Bremelanotide: New Drug Approved for Treating Hypoactive Sexual Desire Disorder.Ann Pharmacother 2020.PubMed 31893927 · doi:10.1177/1060028019899152
Literature retrieved from PubMed on October 18, 2026, favouring human studies and reviews. Numbered markers in the text show which paper supports which statement; uncited entries are background reading.