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Melanotan II (MT-II)

MT-II · Melanotan II

C
Animal replicated
RouteInjectableGray-market only
C
Evidence grade: Animal replicated

Effect demonstrated in multiple animal studies; human data sparse or extrapolated. Grades summarize evidence quality, not whether a compound is appropriate, legal, or risk-free.

At a glance
What it is
Cyclic α-MSH Analog — Non-Selective Melanocortin Agonist — Not FDA Approved — Grade C (Human Phase I) — Melanocortin Agonist, α-MSH Analog, Cyclic Peptide.
Why people use it
Used primarily for skin, hair, and cosmetic use and sexual health.
What the evidence supports
The most important unresolved safety question about Melanotan II: does it cause melanoma? After decades of use, the answer remains genuinely uncertain. Here is the evidence for each position.
If you only read one thing

Melanotan II is a molecule that does three things at once that were never designed to go together: it tans your skin (MC1R), gives you an erection and heightened sexual arousal (MC4R), and suppresses your appetite and raises your blood pressure (MC3R/MC4R sympathetic output). The non-selectivity that made it a problematic drug candidate made it one of the most pharmacologically interesting compounds in the melanocortin literature. It also made it enormously appealing to a community seeking a cosmetic edge — people who wanted a tan, an erection, or appetite suppression discovered they could get all three simultaneously. The central tension of MT-II's story is that the molecule is genuinely active and genuinely dangerous at the same time, and that its most alarming safety signal — the melanoma question — remains genuinely unresolved even after decades of use and case reports.

Route / form

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Evidence fit
Route-specific

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Route caveat
Protocol not standardized

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Protocol anchor
Full dosing section

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Typical dose snapshot
See route notes
Evidence varies by use case
Published literature
2human RCTs0human studies0animal0in vitro
Evidence reality check
Human evidence
2 human studies
2 randomized; 0 observational.
Preclinical base
0 lab signals
0 animal; 0 in-vitro/mechanistic.
Evidence snapshot
The most important unresolved safety question about Melanotan II: does it cause melanoma? After decades of use, the answer remains genuinely uncertain. Here is the evidence for each position.
From the chapter quick-reference block.

Melanotan II is a compound that genuinely works for tanning, genuinely produces erections and sexual arousal, and genuinely raises questions about melanoma that the evidence has not resolved. It is not a fringe compound with no activity — it has Phase I human data, a coherent receptor mechanism, and a pharmacological lineage that produced an FDA-approved drug. It is also one of the most seriously safety-flagged compounds in this reference.

The compound's story resolves here: the University of Arizona team was right that MC1R activation produces tanning. They were also right that non-selective activation of MC3R and MC4R is unavoidable with MT-II. The molecule that was designed to make tanning safer may introduce its own skin cancer risk pathway through MC1R-driven melanocyte proliferation — or it may not, because the evidence is confounded by UV-seeking behavior in the same user population. The melanoma question will not be resolved without a prospective controlled study that has not been done and likely will not be done. In this uncertainty, the practical rule is straightforward: anyone with elevated melanoma risk should not use this compound; anyone who uses it needs active dermatological surveillance.

Properties
Active malignancy: cautionWADA S4✓ Human RCTHPTA: stimulatingNot injectable
Evidence
CAnimal replicated
The Four Receptors and What They Do
MC1R (skin melanocytes): eumelanin synthesis → tanning. This is the intended therapeutic target. MC3R (hypothalamus): energy balance, appetite suppression, metabolic rate. MC4R (hypothalamus, brainstem): sexual arousal in both sexes, appetite suppression, cardiovascular sympathetic output ↑, spontaneous erections in males. MC5R (exocrine glands): sebaceous and exocrine secretion → flushing, facial warmth. MT-II hits all four with similar potency. Every side effect in the profile maps to one of these receptor systems.
MT-II vs MT-1 vs PT-141
Melanotan I (afamelanotide, Scenesse): 13-AA linear analog; highly selective MC1R agonist; FDA-approved for erythropoietic protoporphyria (EPP); no sexual side effects; subcutaneous implant. Melanotan II: 7-AA cyclic analog; non-selective (MC1R + MC3R + MC4R + MC5R); not approved; all systemic side effects. PT-141 (bremelanotide): derived directly from MT-II research on MC4R; selective MC4R agonist; FDA-approved for HSDD in women; no tanning. MT-II is the pharmacological ancestor of PT-141 and the untamed non-selective version of MT-1.
Community Protocol
Loading phase: 100-250 mcg SubQ daily for 10-14 days with UV exposure or sunbed; allows gradual tolerance development and reduces nausea. Maintenance: 250-500 mcg 2-3 times per week with continued UV exposure to sustain tan. Inject before bed to sleep through peak nausea (30-90 min post-injection). Reconstitute 10 mg vial with 2 mL bacteriostatic water (5 mg/mL). Storage: refrigerate reconstituted; protect from light.
Active Malignancy — Hard Stop
MC1R stimulates melanocyte proliferation and melanogenesis. In the context of melanoma — a cancer of melanocytes — this is a theoretical tumor stimulation risk. At least 4 case reports describe melanoma emerging during or after MT-II use. Two systematic reviews disagree on causality (Javed 2013: no conclusive evidence; Wensink 2021: risk probably explained by UV-seeking behavior). The honest answer: causality not proven, mechanism of concern is real, and anyone with dysplastic nevi, personal or family history of melanoma, or >50 moles should not use MT-II. Active melanoma or skin cancer: absolute contraindication.
The Nasal Spray Problem
TikTok-marketed 'Barbie drug' nasal sprays contain Melanotan II. Vial content analysis found 4.32-8.84 mg actual content in vials claiming 10 mg. The nasal route has poor bioavailability compared to SubQ, unpredictable dosing, no sterility standards, and all the same systemic MC4R side effects (including cardiovascular and sexual). MHRA and multiple national health authorities have issued explicit warnings. The nasal spray format is unregulated, underdosed, and adds nasal mucosal delivery of an unsterile peptide on top of all the systemic risks. It is the highest-risk MT-II delivery format.
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