Cyclic heptapeptide analog of α-MSH with broad melanocortin receptor activity
akaMT-IIMT2Melanotan 2Melanotan-II
Class
Melanocortin agonist
Half-life
~30–60 minutes
Route
Subcutaneous (SubQ)
Cadence
Daily
Evidence
Mixed / early human
Overview
Melanotan II is a synthetic peptide developed in the 1980s at the University of Arizona to study melanin production. It's a cyclic, lactam-bridged analog of α-MSH that hits multiple melanocortin receptors at once—MC1R for tanning, MC4R for appetite suppression and sexual arousal, MC3R for metabolic effects. The result: tanning without UV exposure, plus side effects that the original developers didn't anticipate and ultimately couldn't commercialize.
Palatin Technologies (which licensed melanotan II) abandoned clinical development in 2000 after the adverse-event rate—nausea, cardiovascular spikes, unwanted erections—was too high, and switched development to bremelanotide (PT-141), a melanotan II metabolite with reduced MC1R activity.
A 2020 study reported that melanotan II suppressed melanoma progression in animal models, though the mechanistic details and study design require confirmation from the primary literature.
Safety considerations
A few of the safety signals worth knowing — the full list, with dosing context and what to monitor, is inside AIx Core.
Not approved by FDA, EMA, TGA, MHRA, or any regulator for any indication. Illegal to sell for human use in the US, UK, and Australia. What's sold online is unregulated—purity, sterility, and actual peptide content are unverified.
Nausea is near-universal at effective doses. Dorr 1996 trial reported nausea at all tested dose levels. Community reports suggest 65% of users experience nausea at doses >500 mcg, typically starting 30–60 minutes post-injection and lasting 2–4 hours.
Melanoma concern is unresolved. Four case reports describe melanomas in users, but all involved heavy UV exposure at the same time. A 2021 review concluded the melanoma risk is likely UV-driven, not peptide-driven. A 2020 mouse study found melanotan II suppressed melanoma progression. The peptide does darken moles and create new ones, which can obscure melanoma detection—regular dermatology monitoring is critical.
+ 4 more safety notes inside AIx Core →
Commonly monitored
Markers and signals people track when researching Melanotan II.
Mole map / dermatology check-ins—existing moles darken, new moles appear
Blood pressure—MC4R effects can spike BP, especially in first hours post-injection
Erection duration (males)—priapism is rare but a documented risk
Nausea timing and severity—peaks 30–60 min post-injection, dose-dependent, often improves with slower titration (MC4R-mediated via area postrema)
Appetite and food intake patterns
Frequently asked questions
What is Melanotan II?
Cyclic heptapeptide analog of α-MSH with broad melanocortin receptor activity. Melanotan II is a synthetic peptide developed in the 1980s at the University of Arizona to study melanin production. It's a cyclic, lactam-bridged analog of α-MSH that hits multiple melanocortin receptors at once—MC1R for tanning, MC4R for appetite suppression and sexual arousal, MC3R for metabolic effects. The result: tanning without UV exposure, plus side effects that the original developers didn't anticipate and ultimately couldn't commercialize.
How is Melanotan II administered?
Subcutaneous (SubQ), typically daily.
What is the half-life of Melanotan II?
~30–60 minutes — Short plasma half-life, but melanin deposition persists weeks to months.
Is Melanotan II approved for human use?
Melanotan II is investigational — not approved by the FDA, EMA, or MHRA for human use at the time of writing.
What does the evidence show for Melanotan II?
Evidence tier: Mixed / early human. Dorr 1996 Phase I trial (3 healthy males, subcutaneous, 0.01–0.03 mg/kg daily for 2 weeks): all subjects experienced tanning; mild nausea reported at most dose levels; spontaneous penile erections lasting 1–5 hours appeared at all doses, paired with stretching/yawning; two subjects were escalated to 0.03 mg/kg, and one of those two experienced Grade II somnolence/fatigue.
What is commonly monitored when researching Melanotan II?
Commonly tracked markers + signals: Mole map / dermatology check-ins—existing moles darken, new moles appear, Blood pressure—MC4R effects can spike BP, especially in first hours post-injection, Erection duration (males)—priapism is rare but a documented risk, Nausea timing and severity—peaks 30–60 min post-injection, dose-dependent, often improves with slower titration (MC4R-mediated via area postrema), Appetite and food intake patterns.
Open this in AIx Core for the full picture
Mechanism breakdown, receptor pathway diagram, full safety list, monitored items, source citations, and one-tap add-to-protocol. Free with any account.
