Evidence-Based Summary
Chemically, these are near-twins. PubChem lists the same seven-residue cyclic structure for both; melanotan II ends in an amide and bremelanotide in a free acid, and reviews describe bremelanotide as a (carboxylated) metabolite of melanotan II. The regulatory gap is large. Bremelanotide (Vyleesi) was approved by FDA in 2019 after two Phase 3 trials in 1,267 randomized premenopausal women, for acquired, generalized hypoactive sexual desire disorder (HSDD) only. Melanotan II has three tiny 1990s human studies (3 to 10 people each), no approval anywhere in the U.S., an FDA safety-risk listing, and case reports of melanoma, priapism and systemic toxicity in people who injected products bought online. Bremelanotide's approval does not carry over to melanotan II, and no trial has compared the two directly.
Quick Comparison: Melanotan II vs Bremelanotide
A high-level comparison of molecule class, molecular receptor targets, FDA regulatory approvals, and verified clinical programs.
| Feature | Melanotan II | Bremelanotide |
|---|---|---|
| Class | Synthetic cyclic alpha-MSH analogue; unapproved research chemical | Synthetic cyclic alpha-MSH analogue; approved prescription medicine |
| Chemical difference | C-terminal amide (PubChem formula C50H69N15O9) | C-terminal free acid (PubChem formula C50H68N14O10); described as a melanotan II metabolite |
| Target receptors | Several melanocortin receptors, including those for skin pigment and sexual function | Melanocortin receptors including MC3R and MC4R in the brain; pigment effects still occur |
| How it is given | Injected by users of unregulated products; no approved form exists | Subcutaneous autoinjector used as needed before anticipated sexual activity, per the label |
| U.S. regulatory status | Not approved; on FDA's list of bulk substances that may present significant safety risks | FDA-approved 2019 as Vyleesi (NDA 210557) for premenopausal women with acquired, generalized HSDD |
| Strongest human evidence | Three small 1990s studies (3, 10 and 10 participants) | Two identical Phase 3 randomized placebo-controlled trials (RECONNECT) |
| Main safety concerns | Case reports of melanoma, new or darkening moles, priapism, rhabdomyolysis and encephalopathy | Nausea, flushing, headache; transient blood-pressure rise; focal hyperpigmentation |
| WADA status (2026) | Not named; falls under S0 (non-approved substances) | Not named on the 2026 Prohibited List |
Same Melanocortin Core, Small Chemical Change
Melanocortin receptors respond to alpha-MSH, a natural hormone that affects skin pigment, appetite and sexual function. Both peptides copy alpha-MSH's active core in a stable ring shape. Because they hit several of these receptors, neither one acts on only a single body system.
Melanotan II
Primary Target: Multiple melanocortin receptors (non-selective)
Affinity Profile: Potent, non-selective agonist
In the 1996 pilot study it darkened skin and also caused spontaneous erections, yawning and nausea, showing pigment and brain effects at the same time. These are human observations from three volunteers, not a safety profile.
Bremelanotide (Vyleesi)
Primary Targets: Melanocortin receptors, including MC3R and MC4R
Affinity Profile: Melanocortin receptor agonist (label class)
Developed for its effect on brain melanocortin pathways linked to sexual desire. The label still warns of focal hyperpigmentation, showing the pigment-cell effect is reduced but not absent. How it improves desire in HSDD is not fully known.
One Approved Indication vs No Approval
U.S. status checked 11 October 2026 against Drugs@FDA, the current DailyMed label and FDA's compounding safety page. An approval belongs to a named product and use, not to every chemically similar molecule.
Melanotan II Status & Formulations
No FDA-approved medicine contains melanotan II. FDA lists it among bulk drug substances that may present significant safety risks in compounding, citing possible immunogenicity, aggregation and peptide-related impurities, and published reports of melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism. Products sold as "research peptides" or tanning injections are unregulated.
Bremelanotide Status & Formulations
Vyleesi (bremelanotide) injection
Approval History: 2019 (NDA 210557)
Approved Indications: Premenopausal women with acquired, generalized hypoactive sexual desire disorder not caused by another medical or psychiatric condition, relationship problems or a medicine. Not indicated for postmenopausal women, for men, or to enhance sexual performance.
View Regulatory PackageCritical Regulatory Distinction
Being closely related to an approved drug does not make melanotan II approved, tested or safe. Bremelanotide's approval rests on Phase 3 data for one population and one use; it says nothing about tanning, use in men, or products bought online under either name.
Three Tiny Studies vs Two Phase 3 Trials
No trial has compared melanotan II with bremelanotide. The summaries below come from separate studies with different populations and outcomes, so they cannot be ranked against each other.
Melanotan II: 1990s pilot and crossover studies
Dorr and colleagues (1996) gave melanotan II to three healthy men: two developed measurably darker skin, with erections, stretching, yawning and nausea as side effects. Two crossover studies by Wessells and colleagues in 10 men each (1998, 2000) reported drug-induced erections in men with erectile dysfunction, with nausea common. There have been no modern controlled trials, and the compound was never developed into a medicine. Since then, the literature is dominated by case reports in people using unregulated products.
Bremelanotide: RECONNECT Phase 3 program
Two identical 24-week randomized, double-blind, placebo-controlled trials randomized 1,267 premenopausal women with HSDD. Bremelanotide produced statistically significant but modest improvements in a desire score (integrated difference 0.35 points) and reductions in desire-related distress (integrated difference -0.33) versus placebo. Nausea, flushing and headache were more common. The trials were funded by the developer, Palatin Technologies. Earlier studies in men with erectile dysfunction were not taken forward to approval.
Label Warnings vs Case Reports
Bremelanotide's risks were measured in controlled trials and appear on an FDA label. Melanotan II's risks are known mainly from case reports, which can signal danger but cannot give frequencies or prove cause.
Unregulated melanotan products
Case reports describe melanoma, eruptive or darkening moles, prolonged painful erections needing emergency care, and systemic toxicity with rhabdomyolysis and kidney injury after melanotan II injection. Products bought online may not contain what the label says. A 2017 dermatology review counted four case reports of melanoma arising from existing moles during or shortly after melanotan use, while noting that conclusive evidence of a causal link is lacking.
| Safety Consideration | Melanotan II | Bremelanotide |
|---|---|---|
| Source of safety data | Three small studies plus case reports | Phase 3 trials and FDA-reviewed label |
| Common effects | Nausea, yawning and stretching, spontaneous erections (small studies) | Nausea (40% in trials), flushing, injection-site reactions, headache |
| Cardiovascular | Not studied systematically; renal infarction and sympathomimetic toxicity reported | Transient blood-pressure rise and heart-rate fall after each dose; contraindicated in uncontrolled hypertension or known cardiovascular disease |
| Skin pigment | Intended tanning effect; mole changes and melanoma reported | Focal hyperpigmentation (face, gums, breasts) in about 1% of trial patients; more likely with darker skin and daily use |
| Priapism | Several case reports requiring emergency treatment | Not part of the approved female indication |
What Melanotan II and Bremelanotide Have in Common
Where the two compounds overlap in biology, evidence or regulatory context.
Near-identical structure
Both are the same cyclic seven-residue melanocortin peptide; they differ at the C-terminus (amide vs free acid), and reviews call bremelanotide a melanotan II metabolite.
Shared receptor family
Both activate melanocortin receptors, which is why both can affect skin pigment and sexual function.
Nausea is common
Nausea was frequent with melanotan II in the 1990s studies and is the most common reaction in bremelanotide's Phase 3 trials.
Key Scientific & Clinical Differences
Meaningful distinctions in mechanism, strength of evidence, safety and regulatory status.
Approval
Bremelanotide is FDA-approved for one narrow indication; melanotan II has never been approved and is on an FDA safety-risk list.
Quality of evidence
Two Phase 3 trials with more than 1,200 women, versus three studies totalling 23 participants.
Product quality
Vyleesi is manufactured under FDA oversight; melanotan II sold online is unregulated and of unknown purity and content.
Intended use
Bremelanotide is labeled for HSDD in premenopausal women and not for sexual performance; melanotan II is mostly marketed for tanning.
Scientific Comparison vs Clinical Recommendations
Inside Peptides compares scientific evidence, receptor pharmacology, and official regulatory documents to advance public and professional understanding. We do not determine which compound is appropriate for an individual patient, rank medications with arbitrary scores, or recommend initiating or switching treatments.
Decisions about any medicine require a licensed healthcare professional who can weigh personal medical history, contraindications, interactions and monitoring needs. Unapproved peptides have no established safe use, and products sold as “research chemicals” are not the preparations studied in clinical research.
Approved Uses vs Online Claims
A critical scientific distinction between verified, FDA-approved clinical uses and unverified claims circulating on social media and vendor platforms.
Melanotan II is basically the same as an FDA-approved drug, so it is safe
Not supportedFDA lists melanotan II among bulk substances that may present significant safety risks.
Chemical similarity is not evidence of safety. The approval covers Vyleesi, a specific manufactured product, for one use. Melanotan II has never been through equivalent trials, and case reports describe serious harms in users.
Melanotan II gives a safe tan without sun damage
Not supportedNo FDA-approved tanning product contains melanotan II.
The tanning effect was seen in a three-person pilot study. No trial has shown it prevents skin cancer, and melanomas and mole changes have been reported in users.
Bremelanotide boosts sexual performance in anyone
Supported for approved use onlyVyleesi label: indications and limitations of use.
Phase 3 trials showed modest improvements in desire and distress in premenopausal women with HSDD. The label states it is not for men, postmenopausal women, or enhancing sexual performance.
Evidence Strength Across Clinical Domains
Inside Peptides evaluates scientific certainty at the claim level. Because clinical evidence varies significantly depending on the therapeutic endpoint evaluated, each domain is assessed independently.
Hypoactive sexual desire disorder in premenopausal women
Two Phase 3 trials support bremelanotide for this indication, with modest average effects. Melanotan II was never tested for it.
Skin tanning
A three-person pilot shows melanotan II can darken skin; this is not evidence of safe or protective tanning. Bremelanotide is not used or studied for tanning.
Erectile dysfunction
Small studies of both reported erections in men; neither is approved for this use.
Long-term safety
Bremelanotide has controlled-trial and label safety data; melanotan II safety information comes mainly from case reports.
What Research Still Doesn’t Tell Us
Identifying open scientific questions, pending active-comparator trials, and areas where long-term clinical data remain incomplete.
No direct comparison
No study has compared the two peptides in people, so differences in receptor selectivity and side effects come from separate data.
Melanoma risk
Whether melanotan II causes melanoma is unproven; case reports cannot establish cause or frequency.
Metabolism data
The 'metabolite' description comes from reviews; we did not find a primary human study measuring how much melanotan II is converted to bremelanotide.
Industry funding
The bremelanotide Phase 3 trials and early pharmacology were funded or run by the developer; independent replication is limited.
Related Compound Profiles
Individual profiles provide full molecular datasheets, CAS numbers, preclinical histories, and compound monographs.
Related Educational Resources
Scientific & Regulatory References
Every pharmacological mechanism, clinical trial result, and regulatory approval cited on this page is traceable to official FDA prescribing documentation, ClinicalTrials.gov registries, or peer-reviewed medical publications.
-
Pilot Phase I study
Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study.Three healthy male volunteers.
-
Crossover trial
Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study.Ten men with psychogenic erectile dysfunction.
-
Crossover trial
Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction.
-
Two Phase 3 randomized trials (RECONNECT)
Bremelanotide for the Treatment of Hypoactive Sexual Desire Disorder: Two Randomized Phase 3 Trials.Funded by the manufacturer (Palatin Technologies).
-
Early clinical pharmacology
PT-141: a melanocortin agonist for the treatment of sexual dysfunction.Authors from the developer, Palatin Technologies.
-
Case report and discussion
Melanotan Tanning Injection: A Rare Cause of Priapism.Describes bremelanotide as a melanotan II metabolite developed as a sexual stimulant without the tanning effect.
-
Review
Novel Emerging Therapies for Erectile Dysfunction.Full text describes bremelanotide as a carboxylated metabolite of melanotan II, formerly known as PT-141.
-
Case report
Melanoma associated with the use of melanotan-II.
-
Review
Risks of unregulated use of alpha-melanocyte-stimulating hormone analogues: a review.
-
Case report
Melanotan II injection resulting in systemic toxicity and rhabdomyolysis.Product identity confirmed as melanotan II by mass spectrometry.
-
Case report and review
Melanotan II: a possible cause of renal infarction: review of the literature and case report.
-
FDA safety page
Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety RisksContent current as of 22 April 2026; melanotan II entry checked 11 October 2026.
-
FDA Drugs@FDA record
Drugs@FDA: VYLEESI (bremelanotide) injection, NDA 210557Original approval 21 June 2019; checked 11 October 2026.
-
Official U.S. prescribing information
VYLEESI (bremelanotide) injection, current labelLabel version published November 2025; checked 11 October 2026.
-
Chemical database record
Melanotan-II, PubChem CID 92432Molecular formula C50H69N15O9 (C-terminal amide).
-
Chemical database record
Bremelanotide, PubChem CID 9941379Molecular formula C50H68N14O10 (C-terminal free acid).
-
Anti-doping rule
World Anti-Doping Code International Standard: Prohibited List 2026Section S2 lists GHRH and its analogues (e.g. CJC-1293, CJC-1295, sermorelin and tesamorelin); S0 covers pharmacological substances with no current governmental approval for human therapeutic use.