Melanotan I vs Melanotan II
Safety note. Melanotan II is not FDA approved for any use and its safety has not been established. Melanotan I is approved only as a clinician-placed implant for a rare photosensitivity disease, not for tanning. This comparison is educational and is not a protocol or medical advice.
These two peptides are usually discussed as if they were versions of the same product, one milder and one stronger. They are not. They differ in length, in shape, in which receptors they bind, and most consequentially in whether any regulator has ever agreed they are safe enough to sell. One is a prescription implant with trial data behind it. The other is a powder from an anonymous vendor. The gap between them is the story. For the underlying pharmacology of this whole class, start with our tanning peptide guide.
At-a-Glance Comparison
| Factor | Melanotan I | Melanotan II |
|---|---|---|
| Structure | 13-amino-acid linear α-MSH analog | 7-amino-acid cyclic lactam-bridged peptide |
| Receptor target | Relatively MC1R-selective | Non-selective: MC1R, MC3R, MC4R, MC5R |
| FDA status | Approved Oct 8, 2019 (Scenesse) for EPP phototoxicity | Not approved for any use |
| EMA status | Approved 2014 | Not approved |
| Approved form | 16 mg subcutaneous implant, every 2 months | None; sold as lyophilized research powder |
| Potency | Moderate | High; effective at lower doses |
| Nausea | Minimal | Common (MC3R/MC4R) |
| Appetite suppression | Minimal | Common (MC4R) |
| Erectile effects | Not characteristic | Common (MC4R) |
| Human trial data | Randomized controlled trials for EPP | None for any indication |
| Adverse event monitoring | Post-market pharmacovigilance | None |
| Cosmetic tanning use | Not an approved indication | Not approved; the dominant real-world use |
The short version: Melanotan II wins on the one metric users care about and loses on every metric that determines whether a drug is safe to put in your body.
Mechanisms: Structure Determines Everything Downstream
Melanotan I is a linear 13-amino-acid chain, a close structural relative of natural alpha-melanocyte-stimulating hormone (α-MSH) with modifications for metabolic stability. Melanotan II is a truncated 7-amino-acid peptide, cyclized by a lactam bridge that locks it into a rigid conformation. Cyclization is a standard medicinal chemistry move: it raises potency and resists enzymatic degradation. It also, in this case, cost the molecule its selectivity.
Melanotan I favors MC1R, the receptor on melanocytes that controls eumelanin synthesis. Hit MC1R and you get pigment. Melanotan II binds MC1R, MC3R, MC4R, and MC5R without meaningful discrimination. MC3R sits in the hypothalamus and gut. MC4R sits in the central nervous system and governs appetite and erectile response. MC5R sits in sebaceous glands.
So the entire Melanotan II side effect list writes itself from the receptor map. Nausea is MC3R and MC4R. Appetite suppression is MC4R, the same axis the approved obesity drug setmelanotide deliberately targets. Spontaneous erections are MC4R, and that effect was compelling enough that researchers spun it out of the Melanotan II program and developed it into bremelanotide (PT-141), now approved for hypoactive sexual desire disorder. Melanotan II is not a tanning drug with side effects. It is a broad melanocortin agonist that happens to tan. See also our PT-141 vs Melanotan II comparison.
Approval Status: The Asymmetry That Matters
On October 8, 2019, the FDA approved Scenesse (afamelanotide) as a 16 mg subcutaneous implant to increase pain-free light exposure in adults with a history of phototoxic reactions from erythropoietic protoporphyria. The EMA approved it in 2014. EPP is a rare inherited disorder where protoporphyrin builds up in skin and reacts to light, causing severe burning pain. More melanin buys these patients time outdoors.
Read that indication carefully, because vendors quote the approval without it. The approved product is an implant, placed above the anterior supra-iliac crest by a trained clinician every two months, in monitored patients with a diagnosed rare disease. Cosmetic tanning was never studied and is not approved.
Melanotan II has no approval anywhere. The FDA has issued warning letters to distributors, and Australia's Therapeutic Goods Administration has publicly urged consumers to avoid it. There is no manufacturer, no trials, no monograph, and no adverse event reporting pathway. Note the asymmetry this creates in the evidence: a safety signal that would surface in months for an approved drug can go undetected indefinitely for Melanotan II, because no one is collecting the data. Absence of evidence is doing a lot of unearned work in the argument that Melanotan II is fine. For the wider picture, see are peptides legal.
Tanning Efficacy
Both peptides darken skin without UV, and this is the part of the story that is straightforwardly true. Melanotan II does it faster and at lower doses because of its potency and stability advantage. Anecdotally, users report visible change within 1-2 weeks on Melanotan II versus 3-4 weeks on Melanotan I, with pigment fading over roughly 1-3 months after stopping as pigmented keratinocytes turn over and shed.
Both are most dramatic in fair-skinned people who normally burn rather than tan, which is the MC1R-variant population that gets little color from UV. That is also, not coincidentally, the population at highest baseline melanoma risk.
The efficacy claim that does not survive scrutiny is photoprotection. Increased eumelanin absorbs some UV, but the magnitude is modest, comparable to a low single-digit SPF, and it is not a substitute for sunscreen. Most protocols circulating online pair the peptide with sunbeds or sun on the theory that UV activates or deepens the response, so real-world users typically increase their total UV dose while believing they are protected.
Side Effects Compared
Afamelanotide's trial-documented effects are relatively mild: nausea in a minority of patients, headache, fatigue, and implant-site reactions. Generalized skin darkening is the intended effect. Because it is prescribed, patients receive dermatologic monitoring alongside it.
Melanotan II's common effects, reported by most users, are nausea, facial flushing, appetite suppression, spontaneous erections, darkening of moles and freckles, and blotchy pigmentation. Its case-report literature is where the comparison stops being close: melanoma diagnosed after use, dysplastic nevus eruption, ischemic priapism, rhabdomyolysis, renal infarction, and posterior reversible encephalopathy syndrome.
Case reports do not establish causation, and the melanoma reports in particular are confounded by the obvious fact that people who inject tanning drugs also seek sun. The concern that survives that objection is different: Melanotan II changes the appearance of moles across the whole body, and mole change is the signal early melanoma detection depends on. That degrades screening whether or not the drug is carcinogenic. The Skin Cancer Foundation's warning rests on this reasoning. See our peptide side effects guide for how these signals get weighed.
Sexual Function Effects
Melanotan II produces spontaneous erections in men and reported libido increases in both sexes, via MC4R agonism in the central nervous system. Melanotan I does not characteristically do this, because it largely leaves MC4R alone. Some Melanotan II users treat this as a feature.
The serious version of the same mechanism is ischemic priapism, an erection that does not resolve. It is a urological emergency and can cause permanent erectile tissue damage if not treated within hours. It appears in the Melanotan II case-report literature. If the sexual effect is what you actually want, bremelanotide (PT-141) exists as an approved drug developed for that purpose with characterized dosing, which is a strictly better route than a research chemical that also happens to change every mole on your body. See peptides for erectile dysfunction.
Dosage and Administration
These two are not administered in remotely comparable ways, and the difference is not a detail.
Afamelanotide is a 16 mg bioresorbable implant inserted subcutaneously above the anterior supra-iliac crest by a trained clinician, once every two months, under prescription. There is no self-administration and no titration.
Melanotan II has no established therapeutic dose, because there are no human dosing trials for cosmetic use. What circulates online, and we are describing it rather than recommending it, is a loading phase around 250-500 mcg daily until the desired shade is reached, then maintenance around 500-1000 mcg once or twice weekly, reconstituted from lyophilized powder with bacteriostatic water. These numbers come from user forums, not evidence.
The structural problem with self-titration here is that users escalate until they see pigment, and every melanocortin side effect scales with the same dose. Because the vial contents are unverified, the actual delivered dose is unknown regardless of what the syringe says. Our guide to peptide storage and handling covers why lyophilized peptides degrade, and research peptides explained covers the sourcing channel.
Safety Considerations
The single practical point worth carrying away: both peptides darken existing moles, and Melanotan II case reports describe moles enlarging and multiplying. Early melanoma detection is built almost entirely on noticing that a mole changed. A compound that changes all of them at once removes the signal, independent of whether it causes any cancer.
Anyone using either compound cosmetically is doing so outside any monitoring system. Baseline dermatologic mapping before use and periodic skin checks are the minimum a clinician would insist on, and neither is standard practice among gray-market users. The gap between what would make this defensible and what actually happens is the safety story.
Which Should You Consider?
If you have erythropoietic protoporphyria, this is not a choice you make from a comparison table. Afamelanotide is an approved therapy for your condition and the conversation belongs with a specialist.
If you want a cosmetic tan, neither option is what the marketing suggests. Afamelanotide is not available to you. Melanotan I bought as powder online is not afamelanotide in any sense that matters, because the approval attaches to a manufactured, tested, clinician-placed product, not to a molecular formula. And Melanotan II is the compound with the case reports.
The steelman for Melanotan II deserves stating: a fair-skinned person who tans chemically rather than by burning is, mechanistically, avoiding the UV damage that actually causes melanoma. If the product were manufactured to standard, dosed by a clinician, paired with dermatologic monitoring, and combined with strict UV avoidance, that would be a real argument. None of those conditions describe how Melanotan II is actually used. The objection is not to the pharmacology. It is to everything surrounding it.
Verdict
- Evidence and oversight: Melanotan I, decisively — trials, two regulatory approvals, pharmacovigilance.
- Cosmetic potency: Melanotan II, and it is the only category it wins.
- Side effect burden: Melanotan I, by a wide margin, because selectivity is the whole game.
- Real-world availability for tanning: neither, honestly. Afamelanotide is EPP-only; everything else is gray market.
Related reading: Tanning peptides: full guide, Melanotan II peptide profile, PT-141 vs Melanotan II, PT-141 (bremelanotide), GHK-Cu peptide, what are peptides, and peptide side effects.
Frequently Asked Questions About Melanotan
Melanotan I in its approved form (afamelanotide / Scenesse) has a defined safety profile because it went through clinical trials and carries post-market surveillance. Melanotan II has no trials, no manufacturing oversight, and a case-report record that includes melanoma, ischemic priapism, rhabdomyolysis, renal infarction, and posterior reversible encephalopathy syndrome. But the comparison is not apples to apples: the safety data for Melanotan I applies to a clinician-placed implant in monitored EPP patients, not to gray-market Melanotan I powder sold for tanning, which carries the same unknown-content problem as Melanotan II.
Receptor selectivity. Melanotan I is relatively selective for MC1R, the pigment receptor on melanocytes. Melanotan II is a cyclic peptide that binds MC1R, MC3R, MC4R, and MC5R without discrimination. MC3R activation in the hypothalamus and gut drives nausea. MC4R activation in the central nervous system drives both appetite suppression and the erectile response. Those effects are not accidents of contamination or dosing. They are the structural consequence of a non-selective molecule.
Chemically, yes. Afamelanotide is Melanotan I, a 13-amino-acid linear alpha-MSH analog. In practice the two names describe very different products. Afamelanotide means Scenesse, a 16 mg subcutaneous implant approved by the FDA on October 8, 2019 for pain-free light exposure in adults with erythropoietic protoporphyria, placed by a trained clinician every two months. Melanotan I sold online means lyophilized powder from an unregulated vendor. Same molecule on paper, entirely different assurance about what is in the vial.
Melanotan II, by most anecdotal accounts, at lower doses. Its cyclic lactam-bridged structure gives it higher potency and greater metabolic stability than the linear Melanotan I. That potency advantage is inseparable from its selectivity problem, though: the same non-selective binding that makes it tan efficiently is what recruits the MC3R and MC4R effects. Faster tanning and worse side effects come from the same structural property, so "stronger" and "harsher" are not independent variables you can trade off against each other.
No. Afamelanotide is approved only for phototoxicity in erythropoietic protoporphyria, a rare inherited disorder, and is dispensed through certified clinicians under that indication. Cosmetic tanning was never a trial endpoint and is not an approved use. There is no legitimate prescription route to Melanotan I for tanning in the US.
Yes. Melanocortin agonists stimulate melanin production by binding MC1R directly, which is downstream of the UV-damage signal, so pigmentation occurs without sun. That is the actual pharmacology and it is not disputed. Be careful with the common follow-on claim that this makes tanning peptides a safe substitute for UV: increased melanin provides only modest photoprotection, roughly a low single-digit SPF equivalent, and most protocols circulating online pair the peptide with deliberate UV exposure to deepen the result. In practice users tend to add UV rather than replace it.
Neither Melanotan is a controlled substance, so possession is not itself a crime in the US. Both are unapproved drugs when sold for human use, which makes distribution for that purpose illegal, and the FDA has issued warning letters to Melanotan II distributors. Vendors of both use the research-use-only label to shift liability to the buyer. Afamelanotide as an approved product is prescription-only and not obtainable for cosmetic use.
Melanotan I, and it is not close. Afamelanotide has randomized controlled trial data supporting its EPP indication, an FDA approval, an EMA approval dating to 2014, and ongoing pharmacovigilance. Melanotan II has no controlled human trials for any indication, no approval anywhere, and no adverse event reporting system. The evidence gap between them is the entire point of the comparison.