Research and informational content only. Not medical advice. Many peptides discussed on this site are not approved for human use.
Melanotan II
Research PeptideAlso known as: Melanotan-2 · MT-II · MT-2 · MTII · MT2 · Melanotan-II · the Barbie drug · tanning injection
Preliminary Human
There is NO strong_human (adequately-powered, replicated, clinical-endpoint) evidence for any Melanotan II benefit. The entire human efficacy base is two tiny surrogate-endpoint domains, pigmentation (n=3) and erection / desire (n<=20), produced by the single research group that invented the molecule (Hadley / Hruby / Dorr / Wessells, University of Arizona) and never independently replicated. Against that thin efficacy record sits a real and growing safety literature: mass-spectrometry-confirmed rhabdomyolysis, posterior reversible encephalopathy syndrome (PRES), a 30-hour priapism, forensically-confirmed renal infarction, and a biologically plausible (though not causally proven) melanoma / melanocytic-change signal. Multiple national regulators (FDA, MHRA, TGA and others) have issued explicit consumer-safety warnings, and Melanotan II has never been approved by any drug regulator in any country. It is also routinely confused with two genuinely approved relatives, Melanotan I / afamelanotide (Scenesse) and bremelanotide / PT-141 (Vyleesi), the latter differing by only ~1 Dalton, which unit-resolution mass spectrometry cannot resolve.
Melanotan II is unapproved everywhere, and is constantly confused with two approved relatives
Three molecules from the same University of Arizona melanocortin program get blurred together under the label "melanotan," and only Melanotan II is the unapproved one. Melanotan I / afamelanotide (Scenesse) is the LINEAR sibling, EMA- and FDA-approved for the rare disease EPP as a clinic-implanted dose. Bremelanotide / PT-141 (Vyleesi) is the ~1-Dalton derivative (free acid instead of MT-II's amide), FDA-approved for HSDD. Melanotan II itself, the cyclic, more potent, additionally erectogenic analog sold online as a "tanning injection," has NEVER been approved by any drug regulator in any country. The PT-141 confusion is also a quality problem: at m/z ~1025 the ~1-Da difference is below the resolving power of the unit-resolution mass spectrometry behind most gray-market COAs, so what is labeled "MT-II" cannot be cleanly distinguished from bremelanotide (or vice versa) without high-resolution MS.
The harm record is hospital-grade; the only claimed benefit rests on three subjects
Vendors sell Melanotan II as a convenient "safer tan." The evidence does not support that framing. The single tanning claim rests on a phase-I study of THREE men run by the molecule's own inventors, never replicated. Against that sit mass-spectrometry-confirmed rhabdomyolysis with ICU admission, posterior reversible encephalopathy syndrome (PRES), a 30-hour priapism requiring surgery, and forensically-confirmed renal infarction with new-onset hypertension, plus a biologically plausible melanoma / melanocytic-change signal that has prompted dermatology case reports of darkening and eruptive moles. The Swedish Poisons Information Centre alone logged 215 Melanotan II inquiry cases between January 2008 and May 2019. The "safer tan" claim has been explicitly rejected as a myth by the MHRA and TGA, and the product is unlicensed and injected, so identity, dose and purity are unverified per vial. The honest asymmetry: the benefits are tiny and surrogate; the documented harms are serious and real.
Research use only. Not approved for human consumption in any jurisdiction listed here unless the Regulatory Status table below explicitly states otherwise.
Evidence Tier
Preliminary Human
Human Studies
4
FDA Status
Not Authorized
WADA Status
Prohibited (S0)
Mol. Weight
1024.2 Da
Last Reviewed
May 31, 2026
Claimed benefits by evidence tier
Column header colour matches the tier
Preliminary Human3
- Skin tanning (UV-independent pigmentation)
- Erectile function (initiates erections without sexual stimulation)
- Libido / sexual desire
Animal Only1
- Appetite suppression / weight loss
Unsupported2
- Photoprotection / reduced skin-cancer risk
- "Safer tan" / shortcut to a healthy tan (marketing)
Regulatory watch
WADA Prohibited List annual cycle. MT-II remains captured by the S0 catch-all; no melanocortin-specific line has been added.
Worth re-checking each January list cycle for any explicit melanocortin entry that would move MT-II from the S0 catch-all to a named classification.
OPSS / DoD Prohibited Dietary Supplement Ingredients database (last updated 26 May 2026).
The categorical unapproved-drug prohibition stands; monitor for an explicitly named MT-II line item (the JS-gated database did not render one at access time).
· Source
Gray-market peptide enforcement and analytical-chemistry surveillance of falsified peptides.
Surveillance of falsified peptides (under-dosing, solvent and heavy-metal contamination, PT-141 cross-contamination) is an active research area and a likely source of future regulator action.
No sponsor is pursuing approval of Melanotan II itself; the commercial melanocortin pipeline has moved to receptor-selective agents.
Setmelanotide (MC4R-selective) illustrates the modern shift to selective agonists. MT-II is very unlikely to ever be developed as an approved drug.
· Source
About this peptide
Plain English
Melanotan II is an injectable peptide originally designed to give people a protective tan without UV exposure. It mimics a natural hormone (alpha-MSH) that tells skin cells to make the brown pigment melanin. Because the synthetic version is much more stable and reaches the brain, it does not just affect skin: it also acts on brain receptors that control sexual arousal and appetite, which is why users commonly report spontaneous erections, increased libido, nausea, and reduced hunger. It is sold online and in some gyms and salons as a "tanning injection," but it is unlicensed. No regulator has confirmed that any given vial is what it claims to be, is the right dose, or is free of contaminants, and several serious adverse-event reports (rhabdomyolysis, a brain syndrome called PRES, a 30-hour erection, and kidney infarction) are on record.
Technical
Melanotan II (Ac-Nle4-cyclo[Asp5-His6-D-Phe7-Arg8-Trp9-Lys10]-NH2) is a cyclic lactam heptapeptide analog of alpha-MSH(4-10) and a high-affinity, NON-selective agonist at melanocortin receptors MC1R, MC3R, MC4R and MC5R, with negligible activity at the ACTH-selective MC2R. The lactam constraint (Asp->Lys side-chain bridge) and the Nle4 / D-Phe7 substitutions confer proteolytic stability, prolonged action, and increased potency relative to native alpha-MSH. MC1R agonism drives UV-independent eumelanogenesis (pigmentation); central MC4R agonism drives penile erection (via a nitric-oxide-dependent pathway) and appetite suppression. It has no regulatory approval and no validated human subcutaneous pharmacokinetic profile. It is routinely confused with two genuinely approved relatives: Melanotan I / afamelanotide (Scenesse, the linear sibling) and bremelanotide / PT-141 (Vyleesi), the latter differing by only ~1 Dalton (C-terminal -OH vs MT-II's -NH2), a difference unit-resolution mass spectrometry cannot resolve at m/z ~1025.
Mechanism of action
MC1R agonism (skin / melanocytes) -> cAMP -> eumelanin synthesis -> UV-independent pigmentation
MC1R agonism raises melanocyte cAMP, driving eumelanin synthesis and pigmentation independent of UV. This is the strongest of the receptor-level claims: in the Dorr phase-I trial, 2 of 3 subjects developed measurable pigmentation without UV. The endpoint is pigmentation, NOT a clinical photoprotection or skin-cancer outcome. The same MC1R-driven melanogenesis underlies the documented darkening of moles, new pigmented lesions, and mucosal pigmentation.
MC4R agonism (CNS) -> penile erection (NO-mediated) and appetite suppression
Central MC4R activation drives penile erection and sexual desire and suppresses appetite. The erectile effect is central and nitric-oxide-mediated: in anesthetized rabbits, systemic MT-II raised intracavernosal pressure, an effect abolished by the central MC3/MC4 antagonist SHU-9119. The erectile/desire effect has preliminary human surrogate support (RigiScan, self-reported desire); the appetite-suppression outcome is animal-only as a studied endpoint and appears in humans only as a side effect of the ED trials. This is also the mechanism behind the dose-limiting nausea, flushing, and yawning, which are not separable "side effects" but the same central melanocortin pharmacology.
MC3R agonism (CNS, energy homeostasis)
Contributes to energy balance and feeding as part of the non-selective profile. Rodent anorectic effects are attributed mainly to MC4R, with MC3R secondary. No human MC3R data exist for MT-II.
MC5R agonism (exocrine glands)
Weak agonism; MC5R is implicated in sebaceous / exocrine function. In-vitro and animal background only; no source identified for any MT-II-specific human MC5R effect.
MC2R (adrenal / ACTH receptor): effectively no activity
MC2R is selective for ACTH and requires the accessory protein MRAP; alpha-MSH-derived analogs like MT-II do not meaningfully activate it. The practical read is "not a relevant target." No source identified for a specific MT-II MC2R Ki.
Essentially all receptor-level pharmacology comes from in-vitro studies on cloned receptors in transfected cell lines and from rodent / lagomorph functional work. The only human in-vivo readouts are pigmentation and erection; energy-homeostasis and exocrine claims are entirely preclinical. A qualitative rank order of roughly MC1R >= MC4R > MC3R > MC5R >> MC2R is well-supported. GSRS reports Ki values (MC1 0.67 nM, MC4 6.6 nM, MC3 34 nM, MC5 46 nM) citing Wikberg et al. 2000. Other widely-quoted sub-nanomolar values are attributed to Bednarek et al. (1999) but could not be verified against the primary paper and frequently appear as uncited vendor figures. Use the qualitative profile confidently; treat exact nanomolar numbers as needing primary-source verification.
Key studies
Independence warning: most efficacy evidence for this peptide originates from a single research group or single clinical group. Replication by independent groups is limited.
Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study (1996)
Dorr RT, Lines R, Levine N, Brooks C, Xiang L, Hruby VJ, Hadley ME · Life Sciences 58(20):1777-84
- Participants
- 3 healthy men.
- Methodology
- Single-blind, alternating-day saline / MT-II; 0.01 mg/kg SC escalated to ~0.025-0.03 mg/kg.
- Result
- Pigmentation in 2/3 without UV; a "stretching and yawning complex" with spontaneous erections lasting 1-5 h; dose-limiting somnolence / nausea.
Honest read
n=3, single-blind (not double-blind), erection observed not measured, single-center, conducted by the molecule's inventors, NIH/NCI-funded; never independently replicated. This is the foundational human study and it is extremely small.
Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction (double-blind, placebo-controlled crossover) (1998)
Wessells H, Fuciarelli K, Hansen J, Hadley ME, Hruby VJ, Dorr R, Levine N · J Urol 160(2):389-93
- Participants
- 10 men with psychogenic ED.
- Methodology
- Double-blind, placebo-controlled crossover; RigiScan.
- Result
- Erections in 8/10 on MT-II; mean tip rigidity >80% lasted 38.0 min vs 3.0 min placebo (p=0.0045).
Honest read
n=10, surrogate (RigiScan) endpoint with no partnered-sex outcome, same inventor group, short duration. Establishes a real erectogenic effect on a device-measured surrogate, not a quality-of-life outcome.
Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II (2000)
Wessells H, Levine N, Hadley ME, Dorr R, Hruby V · Int J Impot Res 12(Suppl 4):S74-9
- Participants
- 20 men (psychogenic + organic ED).
- Methodology
- Double-blind crossover, RigiScan over 6 h + desire / side-effect questionnaires.
- Result
- Erection in 17/20 without stimulation; increased desire after 68% of MT-II doses vs 19% placebo (p<0.01); 12.9% had severe nausea at 0.025 mg/kg.
Honest read
This is a conference-supplement REVIEW of the group's own subjects, not an independent replication; surrogate endpoints. The 12.9% severe-nausea rate at 0.025 mg/kg is arguably the most useful safety datum in the human literature.
Activation of central melanocortin receptors by MT-II increases cavernosal pressure in rabbits via neuronal NO release (2001)
Vemulapalli R, Kurowski S, Salisbury B, Parker E, Davis H · British Journal of Pharmacology
- Participants
- Anesthetized rabbits.
- Methodology
- Systemic MT-II with and without the central MC3/MC4 antagonist SHU-9119; intracavernosal pressure measurement.
- Result
- MT-II raised intracavernosal pressure; the effect was abolished by SHU-9119 and was nitric-oxide-dependent.
Honest read
Animal mechanism-localization study. Establishes the central MC4R / NO pathway behind the erectile effect; says nothing about human efficacy or safety.
Skin pigmentation and pharmacokinetics of melanotan in humans / MT-II rat pharmacokinetics (1994)
Ugwu SO, Blanchard J, Dorr RT, Levine N, Brooks C, Hadley ME, Aickin M, Hruby VJ · Biopharm Drug Dispos 15(5):383-90
- Participants
- Rats (single 0.3 mg/kg IV dose).
- Methodology
- Single IV dose; HPLC vs bioassay method comparison.
- Result
- Biphasic disposition; HPLC and bioassay correlated (r=0.90).
Honest read
Rat, IV (not the human SC route), method-comparison focus. There is no robust published human SC PK profile for MT-II, a meaningful gap given real-world SC self-injection.
Intermittent MT-II administration and repeated anorexia / fat-weight loss in rodents (MC4R-mediated) (2010)
(rodent appetite study) · PMC2860181
- Participants
- Rodents.
- Methodology
- Intermittent MT-II dosing; food intake and body-composition outcomes.
- Result
- Repeated anorexia and fat / weight loss, attributed mainly to MC4R.
Honest read
Animal-only; not translatable efficacy. The only basis for the "appetite suppression / weight loss" marketing claim, which has zero controlled human weight data.
Research timeline
- 1980
University of Arizona researchers Victor J. Hruby and Mac E. Hadley set out to develop alpha-MSH analogs as sunless-tanning / skin-cancer-prevention agents, because native alpha-MSH degrades too quickly to be a practical drug. Screening identifies [Nle4,D-Phe7]-alpha-MSH (later Melanotan I / afamelanotide). Foundational patents include US 4,485,039 and EP 0292291 (cyclic, lactam-constrained "superpotent" analogs).
- 1989
Al-Obeidi, Hadley, Pettitt and Hruby publish the design of cyclic lactam-constrained superpotent alpha-melanotropins. Melanotan I retains the full 13-residue backbone; Melanotan II condenses the pharmacophore into a cyclic 7-residue lactam. Cyclization bought stability, potency and BBB penetration but removed receptor selectivity, producing the central MC3/MC4 effects (sexual arousal, nausea) that later split the programs.
- 1996
First human MT-II trial (Dorr et al.) reports pigmentation in 2/3 subjects without UV and incidental spontaneous erections. Licensing split via Competitive Technologies (University of Arizona tech transfer): Melanotan I -> Epitan (renamed Clinuvel in 2006); Melanotan II -> Palatin Technologies.
- 2000
Wessells et al. publish the double-blind RigiScan erectile-function studies (1998 and 2000). Palatin ceases MT-II development and pivots to bremelanotide (PT-141), a likely MT-II metabolite differing only by a C-terminal carboxyl in place of MT-II's amide (~1 Da).
- 2008
As unlicensed MT-II spreads online, regulators warn consumers. The UK MHRA states (17 Nov 2008) that Melanotan is unlicensed and its sale/supply/advertising is unlawful (18 reports, 74 suspected reactions). The Competitive Technologies v. Palatin litigation over bremelanotide ownership settles: Palatin keeps bremelanotide, returns MT-II rights, pays US$800,000.
- 2009
Cancer Research UK and dermatology case reports amplify the warning wave. Cousen et al. and Langan et al. document eruptive and rapidly-changing melanocytic naevi after melanotan injection, with histology up to severely dysplastic.
- 2014
Afamelanotide (Scenesse, Clinuvel), the linear Melanotan I sibling, is authorised in the EU for erythropoietic protoporphyria (EPP). This is an approval for the DIFFERENT molecule, not Melanotan II.
- 2019
Two approvals land for MT-II relatives, neither for MT-II itself: bremelanotide (Vyleesi, Palatin) is FDA-approved June 21, 2019 for HSDD in premenopausal women (NDA 210557), and afamelanotide (Scenesse) is FDA-approved October 8, 2019 for EPP. Melanotan II itself remains never-approved, anywhere.
What we don't know
- No human efficacy at clinical endpoints. Tanning evidence is n=3 surrogate; erectile evidence is n<=20 surrogate (RigiScan), with no partnered-intercourse or quality-of-life outcomes.
- No independent replication. The entire human record comes from one group, the inventors.
- No validated human pharmacokinetics for the subcutaneous route actually used (only a rat IV study exists).
- No long-term safety data of any kind, no cohort, no registry follow-up.
- Melanoma causation is unresolved. The signal is biologically plausible and supported by case reports, but no controlled or epidemiological study establishes causation.
- Exact receptor binding constants for MT-II are not reliably verified to primary sources (GSRS Ki values cite Wikberg 2000; the widely-quoted Bednarek 1999 sub-nanomolar figures could not be verified).
- Real-world product identity / dose / purity is unknown per vial, gray-market products are under-dosed and impurity-laden in the limited testing that exists.
- No dose-response or therapeutic-window data in humans beyond the tiny phase-I range.
- Pregnancy, pediatric, and drug-interaction data: none.
- No quantified MT-II-specific stability or shelf-life data in peer-reviewed sources.
Regulatory status
| Jurisdiction | Status | Details | Last Verified | Source |
|---|---|---|---|---|
| United States (FDA) | Not Authorized | NEVER approved by the FDA for any use. Melanotan II is an unapproved new drug; FDA enforcement has been directed at distributors (warning letter to Melanocorp Inc. in 2007 stating MT-II "has not been approved by the FDA or any other regulatory agency"; debarment Docket FDA-2015-N-4169, NOOH letter August 5, 2016). It is sold in the US only as a "research chemical" outside any regulated supply chain. Separately, the US Department of Defense / Operation Supplement Safety (OPSS) prohibits Melanotan II for service members as an unapproved drug under the DoD Prohibited Dietary Supplement Ingredients framework (DoDI 6130.06). The approved relatives are different molecules: bremelanotide (Vyleesi, 2019) for HSDD and afamelanotide (Scenesse, 2019) for EPP. | 2026-05-31 | |
| Canada (Health Canada) | Not Authorized | Classified as a drug; no Drug Identification Number (DIN); not approved for tanning. The Canadian Cancer Society and Health Canada have positioned injectable Melanotan as an unauthorized drug. No dated, melanotan-named Health Canada bulletin was located; the verified position is "drug / no DIN / not approved." Research-market purchase from online vendors is outside the regulatory pathway. | 2026-05-31 | |
| United Kingdom (MHRA) | Prohibited | Unlicensed; the MHRA has stated (17 Nov 2008) that the sale, supply and advertising of Melanotan for human use is unlawful in the UK, and acted to close selling sites (~72 sites). The MHRA received 18 reports describing 74 suspected adverse reactions. The original MHRA press-release URL was not directly accessible; the facts were verified via the Reactions Weekly pharmacovigilance digest and Cancer Research UK coverage. Personal-possession rules differ from supply rules. | 2026-05-31 | |
| European Union (EMA) | Not Authorized | No EMA marketing authorisation for Melanotan II. The related linear analog afamelanotide (Scenesse) IS authorised in the EU (since 2014) for EPP, but that is a different molecule. MT-II non-submission to the EMA is an absence of evidence, not an authorisation. | 2026-05-31 | |
| Australia (TGA) | Not Authorized | Not on the Australian Register of Therapeutic Goods (ARTG). Captured by Schedule 4 (Prescription Only Medicine) of the Poisons Standard by default if supplied therapeutically, so it is illegal to advertise or supply without a prescription. The TGA has issued explicit consumer warnings ("Beware the Barbie drug"), and scheduling was considered by the ACCS/ACMS in November 2017. | 2026-05-31 | |
| WADA | Prohibited (S0) | Prohibited at all times. Melanotan II is captured by Section S0 (Non-Approved Substances) of the WADA 2026 Prohibited List because it has no regulatory approval anywhere and is not enumerated elsewhere (it is not named in S2). The 2026 list took effect 1 January 2026. IMPORTANT: WADA does not publish an explicit "melanotan = S0" line, the S0 classification here is a reasoned conclusion from the verified S0 / S2 category texts, and the 2026 PDF was verified via the Drugs.com WADA mirror rather than the primary PDF. Athletes should verify directly at wada-ama.org/en/prohibited-list before relying on this profile for compliance. | 2026-05-31 |
Safety profile
Reported side effects
- Nausea, vomiting, abdominal pain / cramping, constipation (central melanocortin effect; severe nausea in 12.9% at 0.025 mg/kg in the n=20 human series).
- Appetite suppression.
- Facial flushing, dizziness, headache, anxiety.
- Spontaneous erections; in excess, priapism.
- Darkening of moles and freckles, new pigmented lesions.
- Facial / cutaneous hyperpigmentation and melasma-like changes.
- Oral mucosal pigmentation.
- Muscle pain (and, at high or repeated doses, rhabdomyolysis).
- Yawning and somnolence ("stretching and yawning complex").
Theoretical concerns
Melanoma and melanocytic change (the single most important safety topic)
MT-II clearly stimulates eumelanogenesis and is documented to darken existing nevi and trigger eruptive new nevi, sometimes within 24 hours, with histology reported up to severely dysplastic. Verified melanoma reports in users exist (Paurobally 2011: nevus-to-melanoma ~3 months after use; a Karger case "melanoma associated with MT-II"). Causation is NOT established: no controlled or epidemiological study shows MT-II causes melanoma, and confounders are heavy (concurrent sunbed use, genetic risk, possible pre-existing lesions). Honest position: a biologically plausible signal with concerning case reports, causation not established. Risk is heightened in people with personal/family melanoma history, atypical/dysplastic nevi, or FAMMM syndrome.
Severity: documented
Rhabdomyolysis / sympathomimetic toxicity
A 39-year-old who injected ~6 mg SC (about 6x a typical starting dose) had CPK rise from 1,760 to 17,773 IU/L over 12 h and required 3 days in the ICU; the substance was confirmed as MT-II by mass spectrometry. Documented, dose-related, and life-threatening.
Severity: documented
Posterior reversible encephalopathy syndrome (PRES)
Seizures, visual disturbance and confusion with characteristic posterior white-matter MRI changes have been reported in association with melanotan. A serious neurological event documented in a case report.
Severity: documented
Priapism
Mechanistically expected from MC4R agonism. A 55-year-old had a painful 30-hour erection after 2 mg SC, requiring aspiration, phenylephrine, then operative penoscrotal decompression. A urological emergency.
Severity: documented
Renal infarction and new-onset hypertension
A previously healthy 45-year-old had ~50% of the right kidney infarcted after self-injecting 27 mg SC over 6 months; embolic / coagulopathic workup was negative; the sample was forensically confirmed as MT-II only. Pre-existing hypertension or cardiovascular disease is a precautionary contraindication given sympathomimetic effects and reported vascular events.
Severity: documented
Pregnancy and breastfeeding
No safety data. Precautionary contraindication.
Severity: theoretical
Unregulated product: identity, dose and purity unknown per vial
MT-II is unlicensed everywhere it is sold for tanning and is injected, adding infection and dosing-error risk. Testing shows gross under-dosing (4.32-8.84 mg actual vs 10 mg labeled) and unknown impurities of 4.1-5.9%, plus residual synthesis solvents and toxic elemental impurities (arsenic / lead) in falsified peptides generally. A clean-looking COA cannot exclude these.
Severity: documented
PT-141 / bremelanotide substitution via unit-resolution MS failure
MT-II (C-terminal -NH2, MW 1024.2) and bremelanotide / PT-141 (C-terminal -OH, MW 1025.2) differ by only ~1 Dalton. At m/z ~1025 the two are indistinguishable on unit-resolution mass spectrometry, the instrument behind most gray-market COAs. Because the two share overlapping synthesis and white-labeling supply chains, substitution or cross-contamination is a plausible failure mode a standard COA will not catch. The two compounds have different MC1R (tanning) activity and different regulatory status.
Severity: possible
Contraindications
- Personal or family history of melanoma, atypical / dysplastic nevi, or FAMMM syndrome.
- Pregnancy and breastfeeding (no safety data; precautionary).
- Pre-existing hypertension or cardiovascular disease (sympathomimetic effects; reported new-onset hypertension and vascular events).
- Any use as an approved medicine: Melanotan II is unlicensed in every jurisdiction, so all use is outside a regulated supply chain.
- Note: the safety of the approved, DIFFERENT analog afamelanotide does NOT transfer to illicit MT-II.
Interactions
- No formal human drug-interaction studies exist for Melanotan II; every interaction concern below is mechanistic / theoretical.
- Concurrent UV exposure or sunbed use amplifies the melanocytic / melanoma signal and confounds any "photoprotection" rationale; documented melanoma-associated cases frequently involved concurrent sunbed use.
- Other sympathomimetic or vasoactive agents: theoretical additive cardiovascular effect; one case of new-onset hypertension with renal infarction is on record.
- Erectogenic agents (e.g. PDE5 inhibitors): additive risk of prolonged erection / priapism given MC4R-driven erections; a 30-hour priapism is documented after MT-II alone.
Dosing observed in the literature
This is a record of doses reported in studies and case reports, not guidance. There is no approved dose for Melanotan II and no clinical-trial basis for the "loading / maintenance" protocols circulating online (e.g. daily low-dose "loading" until desired pigmentation, then 1-2x weekly "maintenance"). Those protocols have no validated pharmacokinetic support and no safety validation, and several of the documented harm cases involved self-selected doses far above the small phase-I range. Content is for informational purposes and is not medical advice.
| Route | Range | Context | Source |
|---|---|---|---|
| subcutaneous | 0.01 mg/kg/day escalated to ~0.025-0.03 mg/kg | Phase-I tanning / tolerability study (n=3). 0.025 mg/kg suggested as a ceiling; somnolence at 0.03 mg/kg. | PMID:8637402 |
| subcutaneous | ~0.025 mg/kg single dose | Double-blind erectile-function studies (n<=20). | Source |
| intravenous | 0.3 mg/kg single dose | Rat pharmacokinetics (not human). | PMID:7981427 |
| subcutaneous | 2 mg single dose | Associated with a 30-hour priapism (case report). | PMID:33460908 |
| subcutaneous | ~6 mg single dose | Associated with rhabdomyolysis and ICU admission (case report). | PMID:23121206 |
| subcutaneous | 27 mg cumulative over 6 months | Associated with renal infarction and new-onset hypertension (case report). | PMC |
Stability & handling
- Lyophilized shelf life
- General lyophilized-peptide guidance only: stable for extended periods when dry and stored cold. No MT-II-specific quantified shelf-life curve was located in peer-reviewed sources, treat any specific storage number as general peptide practice, not a MT-II-validated figure.
- Lyophilized storage
- Store cold, typically -20 °C and protected from light. Stable for extended periods when dry.
- Reconstitution diluents
- Bacteriostatic water for injection (standard for multi-dose research vials), Sterile / 0.9% saline (the peptide is water-soluble)
- Reconstituted (refrigerated)
- Refrigerate at 2-8 °C and use within weeks; avoid freeze-thaw cycles.
- Reconstituted (room temp)
- Degradation accelerates at room temperature; do not store reconstituted solution warm.
- OK to refreeze
- No
- Light sensitive
- Yes, protect from light
The indole (Trp) and other residues make the peptide susceptible to photo- and oxidative degradation, so protect from light. The lactam cyclization and D-Phe7 / Nle4 substitutions specifically increase resistance to enzymatic / proteolytic degradation relative to native alpha-MSH (Nle replacing Met4 also removes one classic oxidation site). QC failure modes matter as much as storage for what is actually in the vial: (1) BREMELANOTIDE / PT-141 SUBSTITUTION, MT-II (C-terminal -NH2, MW 1024.2) and PT-141 (C-terminal -OH, MW 1025.2) differ by ~1 Da and are indistinguishable on unit-resolution mass spectrometry at m/z ~1025; high-resolution / accurate-mass MS or MS/MS fragmentation is required. (2) MELANOTAN I vs MELANOTAN II CONFUSION, the linear MT-I / afamelanotide and the cyclic MT-II are routinely conflated in listings simply labeled "melanotan" despite being different molecules with opposite regulatory status. (3) UNDER-DOSING / CONTAMINATION, documented online MT-II content of 4.32-8.84 mg against a labeled 10 mg, plus unknown impurities of 4.1-5.9% and (across falsified peptides generally) residual solvents and toxic elemental impurities (arsenic / lead). (4) ACETATE SALT vs FREE BASE, vendors frequently report weight as free base while supplying the acetate salt, so net peptide content can be lower than the nominal label. Any of these can produce a vial that looks acceptable on a basic COA while differing fundamentally from labeled MT-II.
Frequently asked questions
Is Melanotan II the same as PT-141 / bremelanotide?
No, but they are nearly identical and frequently confused. Bremelanotide is essentially Melanotan II with the C-terminal amide (-NH2) replaced by a free acid (-OH), a ~1-Dalton difference in molecular weight (1024.2 vs 1025.2). Bremelanotide (Vyleesi) is FDA-approved for HSDD; Melanotan II is approved nowhere. Critically, the two are indistinguishable on unit-resolution mass spectrometry at m/z ~1025, so gray-market substitution or cross-contamination is hard to detect on a basic COA.
Is it the same as Melanotan I / Scenesse?
No. Melanotan I (afamelanotide) is a different, LINEAR molecule and is the active ingredient in Scenesse, an approved drug for the rare disease EPP, administered as a clinic-implanted dose. Melanotan II is the unapproved cyclic analog sold online. They are routinely conflated as "melanotan," but they are different molecules with opposite regulatory status.
Does it cause melanoma?
Unproven, but there is a biologically plausible signal. MT-II clearly stimulates melanin production and is documented to darken and trigger new moles, sometimes within 24 hours, and case reports describe melanoma arising in users. But no controlled study establishes causation, and confounders (sunbed use, genetic risk) are heavy. The honest answer: we do not know that it causes melanoma, but it changes moles in ways dermatologists consider concerning, especially in high-risk people.
Is it legal?
It is not an approved medicine in any country. Selling, advertising, or supplying it for human use is unlawful in the UK and Australia, and it is an unapproved new drug in the US. For athletes it is banned at all times by WADA under S0. Personal-possession rules vary by country.
Why do regulators warn against it?
Because it is unlicensed (no one has verified its safety, efficacy, dose or purity), it is self-injected, and it has a real adverse-event record, rhabdomyolysis, PRES, prolonged priapism, renal infarction, and concerning melanocytic / melanoma changes, while its only claimed benefit (a tan) has trivial human evidence (n=3 surrogate).
What should I look for on a Melanotan II COA?
Even a clean-looking COA does not rule out the main failure modes, because the analytics commonly used cannot detect them. (1) HIGH-RESOLUTION mass spectrometry, not unit-resolution MS, because PT-141 / bremelanotide differs from MT-II by only ~1 Da and is otherwise indistinguishable at m/z ~1025. (2) Explicit confirmation it is MELANOTAN II (cyclic) and not MELANOTAN I / afamelanotide (linear), which are conflated in "melanotan" listings. (3) Net peptide content with an explicit SALT-FORM declaration (free base vs acetate), since documented online vials contained 4.32-8.84 mg against a 10 mg label. (4) Impurity and elemental testing, because falsified peptides have shown residual solvents and arsenic / lead. A COA showing only "purity by HPLC" has not meaningfully characterized what is in the vial.
Last researched: May 31, 2026
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