Melanotan 1 vs Melanotan 2: The Approved One Is a Different Molecule, Delivered by Implant, With Skin-Cancer Surveillance Attached

Melanotan 1 and melanotan 2 are not two versions of one drug. The trade-off this page resolves is approval status against access: one is an approved implant a clinician inserts under skin-cancer surveillance, the other is a different molecule, approved nowhere.

The naming invites the error. Melanotan 1 is the market name for afamelanotide, marketed as Scenesse; melanotan 2 is the compound covered in melanotan II: the evidence is present, and it points the wrong way, which sits in our skin and anti-ageing peptides coverage.

Are melanotan 1 and melanotan 2 two versions of the same drug?

No. They are different molecules with different architectures. Afamelanotide is a linear 13-mer, [Nle⁴, D-Phe⁷]-α-MSH, with no lactam bridge and a molecular weight of 1,646.85. Melanotan II is a cyclic lactam heptapeptide, 1,024.18 g/mol, closed by an Asp5→Lys10 bridge. That is a gap of more than 600 daltons and a different ring structure — not a formulation variant, not a second-generation version, and not the same drug at two doses.

The first six rows carry the whole decision, and they are not close. Everything the approved compound has — a molecule, an indication, a delivery method, a monitoring schedule and a registry — the unapproved one lacks entirely.

A note on names, because it is the source of the confusion. Our source record names the approved molecule afamelanotide (Scenesse) throughout; "melanotan 1" is the name it carries in the market this page serves. The numbering implies a sequence — version one, then version two — and there is no such sequence. A linear 13-amino-acid peptide and a cyclic seven-residue lactam are two different chemical objects that happen to act on the same receptor family, in the way that two unrelated drugs can both be beta blockers.

Melanotan 2 is also one dalton from a third molecule, and that one is a prescription drug. PT-141 (bremelanotide) shares melanotan II's backbone, lactam bridge, D-phenylalanine and norleucine, and differs only at the C-terminus — a lysine amide against a free acid, 1,024.18 against 1,025.2, under 0.1%. So the melanocortin group contains two pairs that are constantly confused, and they are confused for opposite reasons: melanotan 1 and 2 are wrongly treated as versions of one thing when they are more than 600 daltons apart, while melanotan 2 and PT-141 are genuinely near-identical and legally opposite.

What did FDA require before approving melanotan 1?

A physician, an implant and eight years of cancer surveillance. Afamelanotide was approved under NDA 210797 on 8 October 2019 for erythropoietic protoporphyria, delivered as a 16 mg subcutaneous implant inserted by a health care professional trained by the manufacturer, above the anterior supra-iliac crest, every two months. Twice-yearly full-body skin examinations are recommended, and FDA required an eight-year minimum prospective registry focused on skin cancer, implant-site reactions and pigmentary changes.

Four things follow from that approval and each of them separates the two compounds.

That registry requirement is the regulator's own assessment of what a melanocortin agonist does to pigmented lesions over time. It applies to the version with a physician, a defined dose and a rare-disease indication. None of it reaches anyone injecting melanotan II at home.

Read the surveillance apparatus as the price of approval rather than as an administrative detail. FDA looked at a melanocortin agonist given to patients who genuinely need it, in a controlled 16 mg implant delivered every two months by someone the manufacturer trained, and still attached a twice-yearly skin examination and eight years of prospective cancer monitoring. The gap between those two administration models is not a matter of convenience or regulatory friction. It is what a regulator concluded was necessary to use this class of drug safely, in a patient who needs it.

Afamelanotide is not the only melanocortin agonist FDA approved in 2019. Bremelanotide cleared review as VYLEESI the same year, and its label attaches its own set of limits. Two approvals in one class, one year apart in the same calendar, and the surveillance each carries is the regulator's read on the class rather than on the individual molecule.

What does the published literature on melanotan 2 document?

Harm, mostly. The melanotan II literature is not a thin evidence base — it is a two-decade international case literature documenting melanoma and melanoma in situ, oral mucosal melanoma, eruptive dysplastic naevi, rhabdomyolysis with a CPK peak of 17,773 IU/L, priapism, renal infarction and posterior reversible encephalopathy syndrome. These are case reports, so they cannot establish incidence, but the direction of the signal is consistent across multiple countries and two decades.

Melanoma and melanoma in situ

Eruptive and dysplastic naevi are the better-documented harm. Hueso-Gabriel et al. 2012 (Actas Dermosifiliográficas, PMID 22425244) is the most fully documented case: a 25-year-old man, phototype II, after four weeks of subcutaneous MT-II, developed "sudden eruption of multiple melanocytic nevi and rapid transformation of existing nevi" — more than 100 naevi, mostly on the back. The ten most atypical were excised: all dysplastic, three with severe dysplasia, plus a pigmented basal cell carcinoma from the shoulder.

Further published cases include Cousen et al. 2009 (Br J Dermatol, PMID 19575725); Schulze et al. 2014 (Eur J Dermatol, PMID 24334249) — eruptive naevi and darkening of pre-existing naevi 24 hours after a single dose; Reid et al. 2013 (Ir Med J, PMID 23914578); Mang et al. 2012 (Der Hautarzt, PMID 23052015); Burian & Burian 2013 (Läkartidningen, PMID 23451671), the first two Swedish cases; and Sivyer 2012 (Dermatol Pract Concept, PMID 23785612) in a teenager with FAMMM syndrome.

Systemic toxicity

The rhabdomyolysis case deserves particular attention in a comparison about administration models. Mass spectrometry confirmed the injected substance was melanotan II — this was not a contaminated or mislabelled product. The molecule itself did it, at a dose the user chose because dosing guidance for an unapproved drug does not exist. The approved compound has a defined 16 mg implant and a two-month interval; the unapproved one has no label to titrate against.

On what this literature is and is not. These are case reports. They establish that these events happened in people using melanotan II; they cannot establish incidence, and melanoma has a long latency with sun exposure and tanning-bed use as confounders in most of these patients. A structured review by Brennan, Wells and Van Hout (Performance Enhancement and Health, 2014) catalogued the harms; it is a narrative review, not a systematic one, and there is no systematic review of melanotan II adverse effects in existence — do not let anyone tell you otherwise in either direction. What can be said is that the signal is consistent, spans multiple countries and two decades, and that FDA independently reached the same list.

Has any trial shown melanotan 2 works for tanning?

No completed randomised controlled trial of melanotan II for tanning exists. ClinicalTrials.gov returns one record for "melanotan" — NCT07437560, a phase 2 study of MT-II as an adjunct to narrowband UVB phototherapy for repigmentation in stable non-segmental vitiligo, sponsored by Hudson Biotech, estimated enrolment 60, currently recruiting, no results. The only other human material is small early-phase work from the University of Arizona in the 1990s.

That early work is Dorr et al. 1996 (Life Sciences, PMID 8637402), a pilot phase 1 study, and Wessells et al. 2000 (Int J Impot Res, PMID 11035391) on erection and sexual motivation. Those two studies are what launched the compound onto the grey market.

They are not an evidence base for chronic self-administration for cosmetic tanning. A pilot phase 1 study establishes tolerability signals in a handful of supervised subjects over a short window; it says nothing about what happens to a fair-skinned person injecting the same molecule for years. The gap between what those papers tested and what the market does with them is the whole problem.

Set that against the approved compound's evidential position, and the asymmetry is stark rather than marginal. Afamelanotide was approved on a measured benefit — pain-free light exposure in erythropoietic protoporphyria — in a defined patient population, with a registry attached to catch what the trials could not. Melanotan II has one recruiting phase 2 study for a different indication, and the marketed use has never been tested at all.

Why does melanotan 2's non-selectivity matter?

Because it explains the harm list. Melanotan II is a non-selective melanocortin agonist: it activates MC1R for pigmentation, MC3R and MC4R for appetite, sexual function and autonomic effects, and MC5R. The tan, the libido effect, the nausea and the priapism are one drug hitting different receptors at once. There is no dose that produces one without risking the others, which means no administration schedule and no sourcing decision improves that trade-off.

Structurally, melanotan II is built from the α-MSH message core, with norleucine at position 4, D-phenylalanine at position 7, and an Asp5→Lys10 lactam bridge closing the ring. The C-terminus is a lysine amide, and that single detail carries the whole identity story against PT-141.

The case literature reads like a scattered collection of unrelated events only if you assume the compound is a pigmentation agent. It is not. Priapism is not an idiosyncratic reaction to a tanning drug; it is MC4R activation. Nausea is the same. Melanotan II is a melanocortin agonist with no receptor selectivity, and the pigmentation is one of four things it does at once — which is why the compound also appears in our libido and sexual wellness peptides coverage rather than only in a skin category.

That non-selectivity is also the reason the comparison on this page cannot be resolved by dose adjustment. A reader who concludes that the approved compound is safer because a clinician controls the dose has half the picture. The other half is that the two compounds are not the same molecule acting on the same receptor set, so "a lower dose of the unapproved one" is not an approximation of the approved one.

Which is legal, and which is banned in sport?

Melanotan 1 is an approved prescription product and melanotan 2 is approved in no country, with five national regulators on record saying so. Ireland's HPRA stated on 10 August 2023 that melanotan II is "not authorised by the HPRA or any medicines regulator to treat any condition" and removed more than 500 listings in a year. Australia's TGA issued 27 infringement notices totalling $101,412 in May 2026. WADA's S0 catch-all prohibits melanotan II at all times.

On FDA's compounding page, current 22 April 2026, melanotan II is not among the fourteen substances in the active Category 2 group. It appears instead in a table headed "Bulk drug substances nominated but withdrawn," which is a procedural event — the nominator withdrew — and not a safety clearance. FDA's evaluation language is retained on that page and is far stronger than the list placement:

"Compounded drugs containing Melanotan II may pose risk for immunogenicity for certain routes of administration due to the potential for aggregation or peptide-related impurities. Published case reports discuss serious adverse events including melanoma, posterior reversible encephalopathy syndrome, sympathomimetic toxidrome and priapism."

That is FDA naming four specific serious harms, and nothing about the move to the withdrawn-nomination table changes it. Melanotan II is not on the 503A bulks list either, has no USP monograph and is not a component of any approved drug, so it cannot be legally compounded and remains an unapproved new drug. See our FDA peptide regulation timeline, compounding pharmacy versus research peptide and are peptides legal.

On sport, the position is asymmetric and only one half of it is documented. Melanotan II is not named on the 2026 Prohibited List, but the S0 catch-all captures "any pharmacological substance... with no current approval by any governmental regulatory health authority for human therapeutic use." Melanotan II holds no approval anywhere, so S0 applies and it is prohibited at all times. For afamelanotide, our fact base carries no anti-doping determination, and we are not going to infer one from its approval status. See do peptides show up on drug tests.

Which is harder to verify, and what does the platform data show?

Melanotan 2 is the one with a verification problem, and it is not the problem most buyers expect. Distinguishing melanotan II at 1,024.18 Da from afamelanotide at 1,646.85 is trivial for any mass spectrometer — more than 600 daltons apart. The hard separation is melanotan II from PT-141 at 1,025.2, about one dalton on 1,024, which requires high-resolution MS or MS/MS fragmentation. The Purity Index records melanotan II at 99.62% across 251 independent tests, and that figure does not reduce the risk that matters.

Peptigrity's melanotan II data comes from ILS, MZ Biolabs, Kovera, Janoshik and Freedom Diagnostics, across 226 verified shops (verified August 2026), with quantity variance running −7.3% to +16% and endotoxin results mostly absent. Melanotan II price data shows 69 shops in stock at a median of $3.80 per milligram, lowest $1.50/mg on a 10 mg vial and highest $9.00/mg, from 173 known shops (verified 10 August 2026). Those figures exclude shipping, taxes and customs, coupon codes, bulk tiers, multi-vial kits and account-gated pricing. They sit inside a platform total of 11,852 independent lab tests across 118 peptides and 530 shops, with 1,283 community reviews (verified August 2026).

No Purity Index score and no price data exist for afamelanotide on this platform, so the second column of that comparison cannot be filled from first-party data. That absence is itself informative: the approved compound reaches patients as a physician-inserted implant rather than as a vial.

Two published analytical studies exist on exactly the one-dalton problem. Mestria et al. (Drug Testing and Analysis, 2021) characterised black-market melanotan II and bremelanotide by LC-HRMS, and Breindahl et al. (Drug Testing and Analysis, 2015) identified and characterised melanotan II products sold illegally online. Their existence tells you the market has an identity problem serious enough for forensic chemists to study.

This is the one compound on this platform where a high purity score should provide no reassurance at all, because the molecule is the problem. The harms in the case literature came from correctly identified, correctly manufactured melanotan II — mass spectrometry confirmed the injected material in the rhabdomyolysis case. A 99.62% pure vial delivers exactly the pharmacology that produced those reports. Compare vendors on the melanotan II compound page, see where to buy melanotan II for the seven vial-level checks, and read mass spectrometry for peptides and how to read peptide lab results for what resolution buys you.

So which should you choose?

There is no choice to make here in the way the question implies, because the two are not interchangeable at any dose. Afamelanotide is an approved implant for erythropoietic protoporphyria, inserted by a trained clinician every two months with twice-yearly skin examinations and an eight-year skin cancer registry attached. Melanotan II is a different molecule, approved in no country, with a two-decade case literature and no completed efficacy trial for the use it is sold for.

The useful way to read this comparison is as a demonstration of what the class costs to use safely. One melanocortin agonist went through a regulator and came out the other side as a physician-inserted implant for a rare metabolic photodermatosis, with a skin examination twice a year and eight years of cancer monitoring. The other is injected at home, for a cosmetic effect, by people with no baseline mole map, in a market where FDA has already prosecuted a seller for claiming it reduces skin cancer risk.

For converting a reconstituted vial into a per-injection volume, the peptide dosing calculator and the reconstitution calculator will do the arithmetic. Neither can supply a dose for melanotan II, because no completed trial has established one, and the rhabdomyolysis patient's 6 mg was described in the case report as six times the recommended starting dose.

The trial that would settle this

No trial has ever compared these two molecules, and the study that would settle melanotan II has to be randomised, controlled and prospective, because its entire safety literature is case reports. Its primary endpoint would be dermatoscopic naevus counts and atypia, since eruptive naevi is the most consistently reported harm; it would run for years with a melanoma registry attached, enrol Fitzpatrick phototypes I and II, and map every mole before the first dose. It will not be run.

There is no sponsor for a cosmetic indication in a compound already prosecuted as an unapproved new drug in multiple jurisdictions. That absence is permanent, and it should be factored into any decision about the compound rather than treated as a temporary gap that better evidence will one day close. The duration row is the one worth dwelling on: the eight-year figure is not a proposal, it is what FDA already required of the approved molecule in patients who need it.

Frequently Asked Questions

Is melanotan 1 the same as melanotan 2?

No. Melanotan 1 is afamelanotide, a linear 13-amino-acid peptide at 1,646.85 Da with no lactam bridge; melanotan 2 is a cyclic lactam heptapeptide at 1,024.18 Da. They are different molecules that act on the same receptor family, not two versions of one drug. The numbering implies a sequence that does not exist.

Is melanotan 1 approved?

Afamelanotide was approved under NDA 210797 on 8 October 2019 to increase pain-free light exposure in erythropoietic protoporphyria, a rare metabolic photodermatosis. It is a 16 mg subcutaneous implant inserted by a health care professional trained by the manufacturer, above the anterior supra-iliac crest, every two months. It is not approved for cosmetic tanning.

Why does the approved one need a doctor to insert it?

That is what FDA required. The approval attaches an implant delivered only by a trained health care professional, a recommended twice-yearly full-body skin examination to monitor pre-existing naevi and new pigmentary lesions, and an eight-year minimum prospective registry focused on skin cancer, implant-site reactions and pigmentary changes. That surveillance is the regulator's assessment of what this class of drug does to pigmented lesions over time.

Is melanotan 2 legal?

It is approved in no country. Regulators in Ireland, the UK, Australia, Denmark and the United States have all stated it is unauthorised, and several have taken enforcement action — Australia's TGA issued 27 infringement notices totalling $101,412 in May 2026. In the United States it has no USP monograph, is not a component of any approved drug and is not on the 503A bulks list, so there is no legal compounding route.

Does melanotan 2 cause melanoma?

Multiple case reports document melanoma and melanoma in situ in users, including oral mucosal melanoma after nasal spray use and five simultaneous primary melanomas in situ in one patient. Case reports cannot establish incidence, and tanning-bed use and sun exposure confound most of them. Much better documented is eruptive and dysplastic naevi: one patient developed more than 100 new moles after four weeks, with severe dysplasia in three of ten excised.

Can a lab test tell melanotan 1 from melanotan 2?

Trivially — they are more than 600 daltons apart, and any mass spectrometer separates 1,024.18 from 1,646.85. The hard discrimination is a different one: melanotan II against PT-141 at 1,025.2, about one dalton apart, which HPLC co-elutes and nominal-mass MS cannot reliably resolve. That separation needs high-resolution mass spectrometry or MS/MS fragmentation.

Where this leaves the pair

The comparison collapses as soon as the molecules are put side by side. A linear 13-mer at 1,646.85 daltons and a cyclic heptapeptide at 1,024.18 are not two versions of one product, and the numbering that suggests otherwise is the single most consequential piece of misinformation about this pair. One of them went through a regulator. The other has been the subject of enforcement action in five countries.

What the approved molecule carries is the part worth taking away. FDA looked at a melanocortin agonist for a rare photosensitivity disorder, in patients who need it, and required that it be delivered as a 16 mg implant by a clinician the manufacturer had trained, every two months, with a full-body skin examination twice a year and eight years of prospective skin cancer monitoring. That is a regulator's own statement about what this receptor family does to pigmented tissue over time.

None of that apparatus reaches anyone self-injecting melanotan II at home for a tan — and the case literature that has accumulated over two decades, in patients whose product was correctly identified by mass spectrometry, is what the absence of that apparatus looks like in practice.

Browse the skin and anti-ageing peptides category, or our complete peptide guide with 118 compounds (verified August 2026). For per-injection volume, use the peptide dosing calculator alongside the reconstitution calculator. Compare shops through independent lab tests and community-verified shop reviews.

This article is for educational and informational purposes only and does not constitute medical advice. Peptides discussed may be investigational compounds not approved by the FDA (or equivalent regulators in your jurisdiction) for human use. Always consult a qualified healthcare provider before using any peptide or research compound. Peptigrity is an independent review platform and does not sell, endorse, or recommend specific products or vendors.