美拉诺坦 II Melanotan II

Melanotan II is a synthetic cyclic heptapeptide that does something no topical tanning product can: it tells your body to produce more melanin from the inside out. It also triggers erections and suppresses appetite — not as side effects, exactly, but as direct consequences of hitting melanocortin receptors that govern all three of those systems. That broad receptor activity is exactly what makes it interesting, and exactly what makes it dangerous.

The compound was developed at the University of Arizona in the 1980s and 1990s as an analog of alpha-melanocyte stimulating hormone (α-MSH), the body's natural pigmentation signal. The research team's original goal was a tanning agent that could reduce UV exposure and skin cancer risk. What they found instead was a peptide with effects far beyond the skin — one that entered human trials briefly, generated serious safety signals, and never made it to approval.^[1]

Today, Melanotan II sits in a legally murky gray zone. It has no FDA approval, no approved compounding pathway in the US, and a documented history of serious adverse events. It's also widely available through research chemical vendors and used by a large number of people who buy it online. If you're reading this page, you probably already know that. What you need is an honest account of what the evidence actually shows.

Key Takeaways

• Melanotan II binds to melanocortin receptors MC1R–MC4R, producing tanning, pro-erectile, and appetite-suppressing effects through a single mechanism.

Human clinical data is extremely limited — one small pilot Phase 1 study from 1996 with only 3 male participants.

The FDA has not approved Melanotan II for any indication; it is not legally available through US compounding pharmacies or licensed clinics.

Serious adverse events including renal infarction and rhabdomyolysis have been reported in case literature.

Melanotan II is structurally and legally distinct from Melanotan I (afamelanotide), which is FDA-approved for a rare light-sensitivity disorder.

Class	Melanocortin Peptide
Structure	Cyclic heptapeptide; Ac-Nle4-Asp5-His6-D-Phe7-Arg8-Trp9-Lys10-NH2
Molecular Target	MC1R, MC2R, MC3R, MC4R (non-selective agonist)
FDA Status	Research only — no approved indication
Administration	Subcutaneous injection
Dose (Human Pilot Study)	0.01 mg/kg subcutaneously[1]
Half-life	~1–2 hours; half-life not established in humans — animal studies suggest rapid metabolism but specific pharmacokinetic data unavailable
Primary Research Areas	Skin pigmentation, sexual dysfunction, appetite suppression

---

Most peptides hit one receptor system. Melanotan II hits four — and the downstream effects of those four receptors touch three completely separate physiological systems. That's not a design flaw; it was the original point. Researchers wanted a molecule potent enough to drive pigmentation without requiring UV exposure. What they got was a molecule that also activates the MC4R pathway, which controls both sexual arousal and energy balance.

Why MC4R activation matters

MC4R (melanocortin-4 receptor) sits primarily in the hypothalamus and plays a central role in regulating appetite, sexual function, and autonomic tone. When Melanotan II activates MC4R, it can trigger spontaneous erections in men — a finding so consistent in the original pilot trial that it became the basis for a separate drug development program that eventually produced bremelanotide (PT-141), which is now FDA-approved for hypoactive sexual desire disorder in women.

That lineage matters. Melanotan II is the parent compound of a drug that actually made it through the FDA process. The problem is that Melanotan II itself is non-selective — it hits all four melanocortin receptor subtypes simultaneously, producing a wider and less predictable effect profile than the more targeted analogs that came after it.

---

Your skin's pigmentation system runs on a hormonal signal called α-MSH (alpha-melanocyte stimulating hormone). When UV light hits your skin, keratinocytes release signals that prompt the pituitary to release α-MSH, which then binds to MC1R on melanocytes — the cells that produce melanin. More α-MSH binding means more melanin production, which means darker skin.

Melanotan II is a superpotent synthetic analog of α-MSH.^[1] Its cyclic lactam structure — Ac-Nle4-Asp5-His6-D-Phe7-Arg8-Trp9-Lys10-NH2 — gives it higher receptor binding affinity and greater metabolic stability than the native α-MSH sequence.^[1] In plain terms: it delivers a stronger, longer-lasting pigmentation signal than your body's own hormone, without requiring UV exposure to trigger it.

But α-MSH doesn't only act on skin. The same receptor family (MC1R through MC4R) is distributed across the brain, adrenal glands, and peripheral tissues. MC4R in the hypothalamus is particularly relevant — it's a major regulator of energy intake and sexual function. When Melanotan II activates MC4R, it suppresses appetite through hypothalamic pathways and triggers the pro-erectile signaling cascade that researchers later isolated and refined into bremelanotide.

The non-selectivity is the core pharmacological issue. You can't get the tanning effect from MC1R activation without also activating MC3R (which affects energy balance and inflammation) and MC4R (sexual function, autonomic tone). That's not how targeted drugs are designed to work, and it's why the research community moved toward more selective analogs.

---

Be clear about what exists here: the human evidence base for Melanotan II is thin. One published pilot Phase 1 trial. A handful of case reports. Animal studies and in-vitro chemistry work. That's it.

The 1996 Pilot Phase 1 Trial

The only published human clinical study enrolled 3 normal male volunteers and administered subcutaneous Melanotan II at 0.01 mg/kg on alternating days (saline or MT-II) in a single-blind design over two consecutive weeks.^[1] That's an extremely small sample — too small to draw conclusions about efficacy or safety in any population.

What the researchers observed: increased skin pigmentation in the treated subjects, and spontaneous penile erections in 2 of the 3 participants within hours of injection.^[1] Nausea was the most frequently reported side effect.^[1] The erection finding was striking enough that it redirected a significant portion of subsequent melanocortin research toward sexual dysfunction applications.

This trial established proof-of-concept that Melanotan II does what it's supposed to do in humans. It established nothing about long-term safety, optimal dosing, or what happens in women, older adults, or people with underlying health conditions.

Animal and Preclinical Data

Zebrafish studies have shown that Melanotan II can reverse short-term high-fat diet-induced memory impairment, suggesting MC receptor involvement in metabolic-cognitive interactions.^[2] This is interesting biology. It's also zebrafish data, which means it's a long way from clinical relevance.

Medicinal chemistry work has focused on developing more selective analogs. A 2022 study using the CLIPS (Chemical Linkage of Peptides onto Scaffolds) strategy replaced Melanotan II's lactam cyclization with xylene-derived thioethers, producing new compounds with binding affinities ranging from low nanomolar to sub-micromolar across melanocortin receptor subtypes.^[3] Separately, a 2024 study explored tryptathionine and 2,2'-bis-indole stapling strategies applied to Melanotan II's scaffold, with implications for developing more stable macrocyclic analogs.^[4] This research is about building better molecules, not validating the original one.

Case Reports: Serious Adverse Events

The case literature is where the picture gets genuinely concerning. A 2020 case report documented renal infarction — a blockage of blood flow to the kidney — in a patient who had been using Melanotan II obtained from a non-medical source.^[5] The same review noted prior reports of Melanotan II-induced rhabdomyolysis (breakdown of muscle tissue) and renal failure.^[5] These are serious, potentially life-threatening events.

Case reports don't establish causation with the certainty of a controlled trial, but they're the best human safety signal we have for a compound that never completed formal clinical development. The pattern — vascular and renal complications — is consistent with the known cardiovascular effects of MC receptor activation on vascular tone.

---

• Long-term safety in humans — The only human trial ran two weeks in three people. There is no data on what happens with months or years of use. None.
• Efficacy in women — The pilot trial enrolled men only. Tanning and sexual effects in women are entirely anecdotal.
• Optimal dosing — The 0.01 mg/kg trial dose is the only published human figure. The ranges circulating in gray-market communities have no clinical trial backing. Mole and melanoma risk — Melanotan II stimulates melanocyte activity broadly. Dermatologists have raised concerns about potential changes in existing nevi (moles), including reports of darkening and growth, but controlled data on melanoma risk does not exist.^[5] No established human dosing data available; dosing is not characterized in clinical trials.
• Cardiovascular safety — The renal infarction case suggests vascular effects that have never been systematically studied. No cardiovascular outcomes data exists.
• Drug interactions — No published interaction data. The MC4R effects on autonomic tone could theoretically interact with antihypertensives and vasoactive drugs, but this is unstudied.

---

There are no published clinical trials establishing a standard dose for Melanotan II beyond the single pilot study's 0.01 mg/kg figure.^[1] The ranges below reflect what gray-market users and some practitioners report, drawn from community consensus and harm-reduction sources. They are not derived from randomized clinical trials.

Not clinical dosing

These ranges are not from controlled clinical trials. They represent gray-market community consensus only. No licensed US clinic can legally prescribe Melanotan II. These figures are provided for informational purposes so that people who are going to use this compound regardless can understand what is being discussed — not as a recommendation.

Community-reported loading doses typically range from 0.25 mg to 0.5 mg subcutaneously per day, with users often starting at the lower end to assess tolerance before increasing. Melanotan II dosing in humans is not established from clinical trials; community-reported doses should be noted as anecdotal and not derived from validated human studies. Maintenance doses reported in harm-reduction communities range from 0.5 mg to 1.0 mg, used less frequently once baseline pigmentation is established. Melanotan II dosing in humans is not established from clinical trials; community-reported doses should be noted as anecdotal and not derived from validated human studies.

The 1996 pilot trial used 0.01 mg/kg — for a 75 kg person, that's 0.75 mg — which puts the community ranges in a roughly similar ballpark, though the trial used alternating-day dosing under medical supervision with saline controls.^[1]

Injection technique in the trial was subcutaneous, consistent with how other melanocortin peptides are administered. Typical injection sites for subcutaneous administration are the abdomen, lateral thigh, or deltoid region, with rotation between sites to minimize local tissue effects.

---

The side effect picture for Melanotan II comes from a mix of the 1996 pilot trial, case reports, and a large body of user-reported experience. Treat these accordingly: the trial data is from 3 people; the case reports reflect serious outlier events; the user reports are uncontrolled and self-selected.

During initial dosing:

• Nausea — The most consistently reported side effect in the pilot trial and in community reports.^[1] Typically occurs within 30–60 minutes of injection and resolves within a few hours. Taking doses at night or with food may reduce severity.
• Facial flushing — Warmth and redness in the face, often accompanying nausea. Linked to vasodilatory effects of MC receptor activation.
• Spontaneous erections — Occurred in 2 of 3 male participants in the pilot trial within hours of injection.^[1] Reported consistently in community use. Can be unwanted and prolonged in some cases.
• Fatigue and yawning — Commonly reported in community use alongside the pro-erectile effect; mechanism not fully characterized.

At ongoing doses:

• Increased skin pigmentation — The intended effect. Darkening typically begins within 1–2 weeks of regular use and is distributed across the body, not just sun-exposed areas. Increased skin pigmentation is the intended pharmacological effect in animal models; however, the specific timeline (1–2 weeks) and distribution pattern in humans are not established in published clinical literature.
• Appetite suppression — MC4R activation reduces hunger signaling in the hypothalamus. Some users report meaningful appetite reduction; this has not been quantified in clinical trials.
• Changes in existing moles — Dermatological case reports have described darkening and enlargement of existing nevi.^[5] Any change in a mole warrants prompt dermatological evaluation.

Rare but serious:

• Renal infarction — Documented in at least one published case report, with prior reports of rhabdomyolysis and renal failure also noted in the literature.^[5] These are severe events. The mechanism is likely vascular — MC receptor activation affects vascular tone.
• Priapism — Prolonged, painful erection not associated with sexual arousal. Given the pro-erectile mechanism of action, priapism has been reported anecdotally in online forums and user reports, though clinical evidence in humans is limited. Cases lasting more than 4 hours have been described in non-clinical sources.

If you develop sudden flank pain, blood in the urine, severe muscle pain, or an erection lasting more than 4 hours after using Melanotan II, go to an emergency room. Don't wait.

---

Legal status in the United States — as of 2026-03

Melanotan II has no FDA approval for any indication. It is not listed as an approved bulk drug substance for compounding under any FDA framework, meaning licensed US compounding pharmacies cannot legally prepare it for patient use. The FDA has issued warnings against the use of Melanotan II products marketed online. Possession is not explicitly criminalized in the US in the way scheduled substances are, but selling it for human use violates federal law. It is sold legally only as a research chemical "not for human use."

The compound occupies a gray zone that's worth understanding clearly. It's not a DEA-scheduled controlled substance, so simple possession doesn't carry the criminal penalties that, say, anabolic steroids do. But it has no legal pathway to human use in the US — no prescription route, no compounding route, no clinical trial access for most people. What exists is a large gray-market research chemical industry selling it in lyophilized powder form, typically in 10 mg vials, for "research purposes."

The FDA has taken enforcement action against companies marketing unapproved Melanotan II products. Patients and providers should consult FDA.gov and the FDA's MedWatch program for current enforcement activity.

Internationally, the status varies. The UK's Medicines and Healthcare products Regulatory Agency (MHRA) has explicitly warned against its use. The regulatory status of Melanotan II varies internationally; some regulatory agencies have issued safety warnings, though specific classifications by individual authorities require verification against current regulatory databases. Australia's Therapeutic Goods Administration (TGA) classifies it as a prescription-only substance. The regulatory status of Melanotan II varies internationally; some regulatory agencies have issued safety warnings, though specific classifications by individual authorities require verification against current regulatory databases. Regulations in other countries should be verified independently.

---

This section exists because people are going to make their own decisions, and harm-reduction information is more useful than pretending the gray market doesn't exist.

What to look for:

• Third-party Certificate of Analysis (COA) — Must come from an independent analytical laboratory, not the vendor's own testing. The COA should confirm peptide identity (typically by mass spectrometry) and purity.
• HPLC purity report — High-performance liquid chromatography purity of at least 98% is the standard for peptides intended for injection. Anything lower increases the risk of impurities with unknown effects.
• Sterile reconstitution — Lyophilized powder should be reconstituted with bacteriostatic water for injection, not tap water or regular saline. Improper reconstitution creates infection risk.
• Cold chain documentation — Peptides degrade at room temperature. Vendors who ship without cold packs or documentation of storage conditions are a red flag.

Red flags:

• No COA or in-house testing only — The most common indicator of a low-quality vendor. Independent verification is the minimum standard.
• Price significantly below market — Real peptide synthesis and independent testing costs money. Unusually cheap product usually means lower purity, wrong sequence, or substituted compound.
• Claims of pharmaceutical grade or FDA-approved — Melanotan II cannot legally carry these designations for human use in the US. Any vendor making these claims is either lying or doesn't understand what they're selling.
• No sterile preparation guidance — Reputable research chemical suppliers provide bacteriostatic water and reconstitution guidance. Those who don't are not operating with user safety in mind.

The gray market for peptides has real quality variance. Contaminated or misdosed product is a genuine risk, and there's no regulatory backstop when something goes wrong.

---

The most important comparison to understand is Melanotan II versus Melanotan I (afamelanotide). They share a name and a research lineage, but they are different compounds with completely different legal and safety profiles. Afamelanotide is FDA-approved under the brand name Scenesse for erythropoietic protoporphyria (EPP), a rare genetic disorder causing extreme light sensitivity. It's delivered as a subcutaneous implant, not an injection, and it's prescribed and administered in licensed clinical settings. If you're interested in melanocortin-based tanning for a medical indication, afamelanotide is the only compound with an established regulatory pathway — and EPP is a narrow indication that most people don't qualify for.

The other relevant comparison is bremelanotide (PT-141), which was developed directly from Melanotan II research. Bremelanotide is FDA-approved as Vyleesi for hypoactive sexual desire disorder (HSDD) in premenopausal women. It's a more selective MC4R agonist than Melanotan II, administered as a subcutaneous auto-injector before sexual activity. If the sexual function application is what you're researching, bremelanotide is the version that made it through the clinical development process.

Melanotan II vs. Related Melanocortin Compounds

Parameter	Melanotan II	Afamelanotide	Bremelanotide
FDA Status	Research only	Approved (EPP)	Approved (HSDD)
Primary Use	Tanning / Sexual function	Tanning (EPP only)	Sexual dysfunction
Receptor Selectivity	Non-selective MC1–4R	MC1R selective	MC4R preferring
Administration	Subcutaneous injection	Subcutaneous implant	Subcutaneous auto-injector
Legal US Access	No	Yes (prescription)	Yes (prescription)

---