Melanotan II

Dosing from the Literature

Published for tanning and libido: 0.01–0.03 mg/kg every other day (Dorr 1996, 3 people) and small erection studies. Not published: any trial of community 'loading' doses.

The trial doses below come from the studies cited; the other figures are what online guides and user forums describe, and no trial has tested them. MT-II is not approved; there is no labeled human dose.

What It Is

Melanotan II (MT-II) is a synthetic cyclic heptapeptide (a chain of 7 amino acids) analog of the endogenous neuropeptide α-melanocyte-stimulating hormone (α-MSH). It was designed and synthesized in the 1980s at the University of Arizona by Mac Hadley, Victor Hruby, and colleagues as part of a research program aimed at developing a "sunless tanning" drug to reduce reliance on UV exposure — the theory being that stimulating endogenous melanogenesis would allow protective melanin pigmentation without the DNA damage of ultraviolet light. The structure is Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys)-NH₂, a lactam-bridged cyclic construct that resists proteolytic degradation and confers dramatically higher potency than native α-MSH.

The design succeeded pharmacologically — MT-II is orders of magnitude more potent than α-MSH (the hormone that tells skin to tan) at melanocortin receptors and produces robust cutaneous pigmentation in humans — but failed to achieve approval. The commercial rights were licensed to Competitive Technologies and development was pursued for years without crossing the regulatory finish line. Two related molecules did reach clinical use, both approved by the FDA in 2019: afamelanotide (Melanotan I, brand name Scenesse), the earlier linear α-MSH analog that MT-II was built from, for erythropoietic protoporphyria, and bremelanotide (PT-141), MT-II's carboxylate derivative, for hypoactive sexual desire disorder in premenopausal women (King et al., 2007; Scenesse and Vyleesi labels).

MT-II itself remained in research-chemical and gray-market channels. In those channels, it became one of the most popular non-approved peptides — used for cosmetic tanning, appetite suppression, and both male erectile dysfunction and female sexual dysfunction. That history is largely responsible for its appearance in the Kalios database: it is widely used in community settings, has a genuinely substantial early-phase human research record, and carries serious safety signals (melanoma case reports, atypical nevus transformation, priapism, rhabdomyolysis) that are important to document honestly.

MT-II is non-selective across the melanocortin family: it binds MC1R (skin pigmentation), MC3R and MC4R with high affinity (King et al., 2007) and also stimulates MC5R (Mallory et al., 2021; PMC7930850). Its derivative PT-141 (bremelanotide) is not selective either: its label lists activity at MC1R, MC4R, MC3R, MC5R and MC2R, in that order of potency, with MC1R and MC4R binding most relevant at the labeled dose (Vyleesi label). Melanotan II's non-selectivity brings tanning, appetite suppression and sexual effects together (Sivyer, 2012), along with the nevus changes described in predisposed users (Cardones & Grichnik, 2009).

Mechanism of Action

Melanotan II is a non-selective melanocortin-receptor agonist (Wessells et al., 2000; PMID 11035391) with high affinity for MC1R, MC3R and MC4R (King et al., 2007; PMC2694735), and it also stimulates MC5R (Mallory et al., 2021; PMC7930850). Melanocortins act on MC1R in the skin to darken it, and on MC3R and MC4R in the central nervous system to cause sexual arousal and erection (Mallory et al., 2021).

• MC1R agonism (skin pigmentation — the primary effect) — MC1R activation switches on tyrosinase and other melanin-making enzymes, increasing eumelanin and skin pigmentation (Mallory et al., 2021; PMC7930850). In the pilot study, MT-II increased pigmentation of the face, upper body and buttock in two of three men (Dorr et al., 1996; PMID 8637402).
• MC4R agonism (central appetite + sexual function) — In animal studies MC4R is emerging as the main receptor behind melanocortin-induced erections (King et al., 2007; PMC2694735), and in rats MT-II caused erections by acting in the brain and spinal cord, not the penis (Wessells et al., 2003; PMID 12710982). The melanocortin system also regulates food intake (King et al., 2007). MT-II engages MC4R non-selectively (Wessells et al., 2000; PMID 11035391), and so does its derivative bremelanotide (Vyleesi label).
• MC3R agonism (role unclear) — The brain carries mainly MC3 and MC4 receptors, and MT-II binds MC3R about as strongly as MC4R; MC3R's role is poorly understood, and in rats, blocking forebrain MC3R increased MT-II's erections (King et al., 2007).
• BP and HR (sympathetic outflow) — In a published case, a man who injected 6 mg had signs of sympathomimetic excess, with a heart rate of up to 146 bpm and blood pressure of 151/85 mmHg (Nelson et al., 2012; PMID 23121206). Its derivative bremelanotide transiently raises systolic blood pressure by up to 6 mmHg at its labeled dose (Vyleesi label).
• Anorectic effect — Decreased appetite was reported more often after MT-II than after placebo, and more at higher doses, in men with psychogenic erectile dysfunction (Wessells et al., 1998; PMID 9679884; King et al., 2007).
• Pigmentation versus sexual effect timing — In the pilot, increased pigmentation was measured a week after the last of five doses, while spontaneous erections came and went for 1–5 hours after each dose (Dorr et al., 1996; PMID 8637402); in the 1998 trial, erections began 15 to 270 minutes after an injection (King et al., 2007).
• α-MSH biological context — α-MSH is one of the peptides cut from the POMC (proopiomelanocortin) gene product; they share a His-Phe-Arg-Trp "core" that MT-II also carries, and MT-II's affinity for MC4R is 10–100 times that of α-MSH (King et al., 2007).

What the Research Shows

Melanotan II's human evidence is small and early: a pilot tanning study in 3 men (Dorr et al., 1996) and placebo-controlled crossover studies of erections in 20 men with erectile dysfunction (Wessells et al., 2000), from the group that designed it. No Phase 3 trial is registered on ClinicalTrials.gov. It has never been FDA-approved.

• Phase 1 pilot (Dorr et al., Life Sci 1996; PMID 8637402) — 3 normal male volunteers; SubQ 0.01–0.03 mg/kg alternating-day dosing over 2 weeks. Two of the three had increased pigmentation of the face, upper body and buttock. Side effects: "stretching and yawning complex" correlated with spontaneous penile erections 1–5 hours after dosing. The authors conclude that MT-II tans human skin after only 5 low doses given every other day by subcutaneous injection.
• Phase I/II erectile dysfunction (Wessells et al., J Urol 1998; PMID 9679884) — Double-blind placebo-controlled crossover in men with psychogenic ED. Erections achieved in responders without sexual stimulation; established proof-of-concept for melanocortin agonism in ED.
• Organic ED (Wessells et al., Urology 2000; PMID 11018622) — Men with organic ED. Increased erectile response plus increased sexual desire (68% of MT-II doses vs 19% placebo, p<0.01).
• Human sexual motivation review (Wessells, Int J Impot Res 2000; PMID 11035391) — 20 men with psychogenic and organic ED, double-blind placebo-controlled crossover. 17 of 20 achieved erection without sexual stimulation; mean 41 min Rigiscan tip rigidity >80%. At 0.025 mg/kg, 12.9% severe nausea.
• Discovery paper on sexual function (Hadley, 2005; PMID 15996790) — Recounts that MT-II's sexual effects were discovered by accident during studies of human skin tanning, and reports that it enhanced erectile activity in men and sexual desire and genital arousal in women.
• UV + melanotropin synergy (Dorr et al., 2004; PMID 15262693) — In three phase 1 studies of Melanotan I (afamelanotide, not MT-II), the peptide plus UV-B light or sunlight tanned skin more than light alone. Underpinned the "tan enhancer" positioning.
• Melanocortin agonists in sexual dysfunction review (Ückert et al., 2014; PMID 25096243) — Comprehensive review of melanocortin agonists in male and female sexual dysfunction contexts, placing MT-II alongside bremelanotide.
• Melanoma/nevus case series (Cardones 2009; Nolte 2015; various dermatology case reports) — Multiple case reports describe atypical nevus transformation, dysplastic nevi, and melanoma-arising-from-mole following MT-II or Melanotan I use. The 2012 case report of a teenager with FAMMM syndrome (Sivyer) remains the most-cited alarm publication (PMC3663356).
• Eruptive dysplastic nevi following Melanotan — Case series documenting rapid appearance of new atypical nevi during Melanotan use.
• Systemic toxicity case (Nelson et al., 2012; PMID 23121206) — Melanotan II injection resulting in systemic toxicity and rhabdomyolysis in a 39-year-old man after a 6 mg SubQ dose, six times the starting dose he said he had been told to use.
• Priapism case reports (PMC7930850) — Melanotan tanning injection as cause of priapism requiring cavernosal aspiration, phenylephrine, and in one case operative penoscrotal decompression.
• Epidemiological review (Gorrie 2015) — "An unhealthy glow? A review of melanotan use and associated clinical outcomes" summarized the pattern of adverse events and cosmetic/sexual use.

Human Data

Small but real:

• Pilot Phase 1 tanning (Dorr 1996; N=3) — Foundational pigmentation demonstration.
• Phase 1/2 ED (Wessells 1998, 2000; N≈20) — Erectile response demonstrated.
• UV + Melanotan I combination (Dorr et al., 2004) — The 2004 light-combination studies tested Melanotan I (afamelanotide), not MT-II: with UV-B light or sunlight it tanned skin more than light alone.
• Fitzpatrick skin type II/III characterization — Tanning response strongest in medium-fair skin types, weaker in very fair (Type I) and very dark (Type V/VI) individuals.
• Women with sexual dysfunction (preliminary) — Early studies of melanocortin agonists in female sexual dysfunction provided signal that ultimately led to bremelanotide's HSDD Phase 3 program.
• No Phase 3 — Development program never advanced to registrational trials for any indication.
• Case series (Gorrie 2015 and subsequent) — Multi-country case series documenting dermatologic adverse events and sexual/tanning misuse patterns.
• Poison control / MHRA registries — UK MHRA and equivalent bodies have accumulated case data on acute toxicity, supporting ongoing warnings against consumer use.

Large absence: randomized controlled trials at modern regulatory scale for any indication. What MT-II has instead is a relatively narrow early-phase database and a broader case-series signal of harm that never found a counter-weight in Phase 2/3 efficacy programs.

Reconstitution & Storage

Sellers list Melanotan II as a freeze-dried powder, often in 10 mg vials (Sivyer, 2012). There is no approved, pre-mixed product.

• Reconstitution — A seller's guide and user-forum posts describe adding the bacteriostatic water slowly down the inside wall of the vial rather than onto the powder, then rolling or swirling the vial rather than shaking it; the seller's guide describes the finished solution as clear.
• Storage — Seller and guide listings disagree. For the powder they list refrigeration at 2–8°C or a cool, dark place; for the mixed solution, 2–8°C for anywhere from 1 week to 30–60 days, and about 24 hours at room temperature. A seller's guide says not to freeze it.
• Injection sites — Online guides and user-forum posts describe injecting under the skin of the abdomen or upper thigh.
• Timing — Online guides describe evening injections, so the nausea passes during sleep; the man in a 2021 priapism case report injected at bedtime for the same reason (Mallory et al., 2021; PMC7930850).
• Inspection — A seller's guide describes a properly mixed solution as completely clear, with no cloudiness, discoloration or particles.

→ Calculator — vial-to-syringe math

Side Effects & Risks

Reported side effects range from common ones, such as nausea (Wessells et al., 2000), to rare, severe ones described in case reports: melanoma (Paurobally et al., 2011), priapism (Mallory et al., 2021; PMC7930850) and rhabdomyolysis (Nelson et al., 2012).

• Nausea and vomiting — Nausea and yawning were frequent in the erection studies; at 0.025 mg/kg, 12.9% of subjects had severe nausea (Wessells et al., 2000; PMID 11035391). In the 1998 study, nausea rose with dose, and an early self-experimenter who took twice the intended dose had nausea and vomiting (King et al., 2007). In a trial of MT-II's derivative bremelanotide, 8 mg of ondansetron taken 30 minutes before the dose did not reduce nausea in 228 healthy women (Vyleesi label).
• Facial flushing / warmth — Listed with nausea, fatigue and dizziness among the reported side effects of Melanotan products (Mallory et al., 2021; PMC7930850).
• Stretching / yawning complex — In the original pilot, a stretching and yawning complex appeared to coincide with the onset of spontaneous erections (Dorr et al., 1996); stretching and yawning were more frequent than with placebo in the erection trials (Wessells et al., 1998).
• Appetite suppression — Decreased appetite was reported more often after MT-II than placebo (Wessells et al., 1998), and suppressed appetite is one reason it was nicknamed the "Barbie drug" (Sivyer, 2012).
• Cardiovascular / BP elevation — In a published case, a man who injected 6 mg had a blood pressure of 151/85 mmHg and a heart rate of up to 146 bpm, with signs of sympathomimetic excess (Nelson et al., 2012). MT-II has no label; its derivative bremelanotide's label contraindicates it in uncontrolled hypertension or known cardiovascular disease (Vyleesi label).
• Hyperpigmentation — generalized and focal — Generalized skin darkening, seen in the pilot (Dorr et al., 1996) and in case reports, where it faded over the months after the injections stopped (Sivyer, 2012). Focal darkening of the face, gums and breasts is a labeled side effect of the related bremelanotide, more common with daily dosing, and it did not always resolve after stopping (Vyleesi label).
• Nevus darkening / atypical nevus transformation — Two case reports describe existing nevi that darkened and grew, and new atypical nevi: in a 40-year-old man with past melanoma and multiple dysplastic nevi who injected synthetic α-MSH (Cardones & Grichnik, 2009), and in a 16-year-old with FAMMM syndrome who injected 0.5 mg of Melanotan II daily and used a sunbed, whose enlarging nevus proved dysplastic (Sivyer, 2012). In both, the nevi lightened after the injections stopped.
• Melanoma (case reports) — Melanoma has been reported in Melanotan users (Paurobally et al., 2011). Case reports cannot show cause; Cardones and Grichnik conclude that synthetic α-MSH peptides can drive the growth of neoplastic melanocytes in predisposed patients, which could raise melanoma risk (Cardones & Grichnik, 2009).
• Priapism — A 2021 case report counts two earlier reports of ischemic priapism after MT-II injection. In its own case, a 55-year-old man's erection lasted 30 hours after a 2 mg injection; cavernosal aspiration, irrigation and phenylephrine failed, he needed surgery (penoscrotal decompression), and he was left with erectile dysfunction (Mallory et al., 2021; PMC7930850).
• Rhabdomyolysis (reported) — A published case: systemic toxicity with sympathomimetic excess, rhabdomyolysis and kidney dysfunction after 6 mg SubQ in a 39-year-old man, who spent 3 days in intensive care (Nelson et al., 2012).
• Gray-market purity — Products bought online are unregulated, and their purity and dose are unknown (Mallory et al., 2021; PMC7930850); the UK MHRA has warned of their potential impurity (Langan et al., 2010).
• Regulatory warnings — The UK MHRA has warned about these unlicensed products (Langan et al., 2010), the FDA and several European authorities have warned against their use and sale (Mallory et al., 2021; PMC7930850), and Australia's TGA urges consumers to avoid it.
• Contraindications — MT-II has no label, so it has no official contraindications. Case-report authors single out people with dysplastic nevi or previous melanoma (Cardones & Grichnik, 2009), and its derivative bremelanotide is contraindicated in uncontrolled hypertension or known cardiovascular disease (Vyleesi label).

Supportive Nutrition & Supplements

• Nicotinamide (500 mg BID) — In the ONTRAC trial, nicotinamide 500 mg twice daily for 12 months lowered the rate of new nonmelanoma skin cancers by 23% in 386 adults who had had at least two in the previous 5 years (Chen et al., 2015). The trial did not involve MT-II.

What to Expect — Timeline

The timings below come from the trials and case reports cited.

• First dose — In the trials, nausea, stretching and yawning were reported more often after MT-II than placebo (Wessells et al., 1998); erections began 15 minutes to 4.5 hours after an injection (King et al., 2007) and came and went for 1–5 hours (Dorr et al., 1996).
• Week 3 — In a case report, a 16-year-old injecting 0.5 mg daily and using a sunbed two to three times a week noticed general tanning and darker moles within three weeks (Sivyer, 2012).
• After stopping — In the case reports, the tan faded and darkened nevi lightened over the following months (Sivyer, 2012; Cardones & Grichnik, 2009).

Quick Compare — Melanotan II vs PT-141 vs Afamelanotide vs Nicotinamide

The most relevant comparators for MT-II are its two molecular cousins (PT-141 for sexual function, afamelanotide for tanning/photoprotection) and the non-drug skin-cancer chemo-prevention benchmark (nicotinamide).

Practical interpretation:

• MT-II vs PT-141 — PT-141 (bremelanotide) is MT-II's carboxylate derivative (King et al., 2007), and its label also describes non-selective action, MC1R most potent (Vyleesi label). It is FDA-approved, with a labeled dose, for premenopausal women with hypoactive sexual desire disorder; MT-II has no approved use.
• MT-II vs afamelanotide — Afamelanotide is FDA-approved only for adults with phototoxic reactions from erythropoietic protoporphyria, as a 16 mg implant every 2 months, and its label recommends a full-body skin examination twice a year (Scenesse label).
• Cosmetic tanning use case — No melanocortin agonist is FDA-approved for cosmetic tanning; Scenesse's label covers erythropoietic protoporphyria only (Scenesse label).
• Skin cancer prevention — In the ONTRAC trial, nicotinamide 500 mg twice daily for 12 months lowered the rate of new nonmelanoma skin cancers by 23% in 386 adults with at least two in the previous 5 years (Chen et al., 2015). The trial did not involve MT-II.

→ See full PT-141 profile  •  → See Melanotan I / afamelanotide profile

Practical User Notes

• Loading then maintenance — Online guides and user-forum posts describe daily injections of 250 mcg–1 mg for one to four weeks, then 250 mcg–1 mg once or twice a week; the figures vary widely between sources.
• Injection technique — Online guides and user-forum posts describe injecting under the skin of the abdomen or upper thigh with an insulin syringe.
• Storage — Seller and guide listings disagree on how long a mixed vial keeps at 2–8°C: from 1 week to 30–60 days.

Bloodwork & Monitoring

No trial, label or guideline sets monitoring for MT-II. The pilot tanning study measured skin color by reflectance and graded side effects on WHO scales in 3 men (Dorr et al., 1996); the erection studies recorded penile rigidity with RigiScan for 6 hours and side effects by questionnaire in 20 men (Wessells et al., 2000; PMID 11035391).

Commonly Stacked With

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Legal Status

Related Compounds

The two approved melanocortin children and the other peptides users reach for instead of MT-II.

Next Steps

References

1. Dorr RT, Lines R, Levine N, Brooks C, Xiang L, Hruby VJ, Hadley ME. Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study. Life Sci. 1996;58(20):1777-1784. PMID: 8637402.
2. Wessells H, Levine N, Hadley ME, Dorr R, Hruby V. Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II. Int J Impot Res. 2000;12 Suppl 4:S74-S79. PMID: 11035391.
3. Wessells H, Gralnek D, Dorr R, Hruby VJ, Hadley ME, Levine N. Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction. Urology. 2000;56(4):641-646. PMID: 11018622.
4. Wessells H, Fuciarelli K, Hansen J, Hadley ME, Hruby VJ, Dorr R, Levine N. Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study. J Urol. 1998;160(2):389-393. PMID: 9679884.
5. Hadley ME, Dorr RT. Melanocortin peptide therapeutics: historical milestones, clinical studies and commercialization. Peptides. 2006;27(4):921-930. PMID: 16412534.
6. Wessells H, Hruby VJ, Hackett J, Han G, Balse-Srinivasan P, Vanderah TW. Ac-Nle-c[Asp-His-D-Phe-Arg-Trp-Lys]-NH2 induces penile erection via brain and spinal melanocortin receptors. Neuroscience. 2003;118(3):755-762. PMID: 12710982.
7. Dorr RT, Ertl G, Levine N, et al. Effects of a superpotent melanotropic peptide in combination with solar UV radiation on tanning of the skin in human volunteers. Arch Dermatol. 2004;140(7):827-835. PMID: 15262693.
8. Cardones AR, Grichnik JM. Alpha-melanocyte-stimulating hormone-induced eruptive nevi. Arch Dermatol. 2009;145(4):441-444. PMID: 19380666.
9. Paurobally D, Jason F, Dezfoulian B, Nikkels AF. Melanotan-associated melanoma. Br J Dermatol. 2011;164(6):1403-1405. PMID: 21564053.
10. Sivyer GW. Changes of melanocytic lesions induced by Melanotan injections and sun bed use in a teenage patient with FAMMM syndrome. Dermatol Pract Concept. 2012;2(3):10. PMC3663356.
11. Langan EA, Nie Z, Rhodes LE. Melanotropic peptides: more than just "Barbie drugs" and "sun-tan jabs"? Br J Dermatol. 2010;163(3):451-455. PMID: 20545686.
12. Nelson ME, Bryant SM, Aks SE. Melanotan II injection resulting in systemic toxicity and rhabdomyolysis. Clin Toxicol (Phila). 2012;50(8):729-730. PMID: 23121206.
13. Melanotan tanning injection: a rare cause of priapism. Case report. 2021. PMC7930850.
14. Gorrie S, Elwes R, Hardman G, Stratigos AJ. An unhealthy glow? A review of melanotan use and associated clinical outcomes. Australas J Dermatol. 2015;56(3):e66-e71.
15. Hadley ME. Discovery that a melanocortin regulates sexual functions in male and female humans. Peptides. 2005;26(10):1687-1689. PMID: 15996790.
16. King SH, Mayorov AV, Balse-Srinivasan P, Hruby VJ, Vanderah TW, Wessells H. Melanocortin receptors, melanotropic peptides and penile erection. Curr Top Med Chem. 2007;7(11):1098-1106. PMC2694735.
17. Ückert S, Bannowsky A, Albrecht K, Kuczyk MA. Melanocortin receptor agonists in the treatment of male and female sexual dysfunctions: results from basic research and clinical studies. Expert Opin Investig Drugs. 2014;23(11):1477-1483. PMID: 25096243.
18. Lengyel I. Melanotan-II (MT-II): a safety perspective on an unlicensed product. Drug Test Anal. 2015;7(11-12):989-994.
19. Chen AC, Martin AJ, Choy B, Fernandez-Penas P, Dalziell RA, McKenzie CA, Scolyer RA, Dhillon HM, Vardy JL, Kricker A, St George G, Chinniah N, Halliday GM, Damian DL. A phase 3 randomized trial of nicotinamide for skin-cancer chemoprevention (ONTRAC). N Engl J Med. 2015;373(17):1618-1626. PMID: 26488693. (Comparator reference — nicotinamide NMSC chemoprevention.)
20. MHRA. Unlicensed Melanotan products warning. UK Medicines and Healthcare products Regulatory Agency advisories.
21. FDA. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the FD&C Act (503A categories list), versions updated April 15, April 22 and May 14, 2026. fda.gov/media/94155/download. Read October 3, 2026. (Notice that 12 peptides would leave Category 2 because their nominations were withdrawn; their removal; GHK-Cu, except injectable, back in Category 1.)
22. Cosette Pharmaceuticals. VYLEESI (bremelanotide injection), for subcutaneous use, prescribing information. NDA 210557; initial U.S. approval 2019; revised 03/2024. DailyMed set ID f1d0c1b5-2f39-4bad-a6a4-0066e3ad5dcf (version 1, published November 18, 2025). dailymed.nlm.nih.gov. Read October 3, 2026.
23. Clinuvel Inc. SCENESSE (afamelanotide) implant, for subcutaneous use, prescribing information. NDA 210797; initial U.S. approval 2019. DailyMed set ID 94f53286-11dd-7fbb-e053-2a95a90a7c48 (version 11, published May 13, 2026). dailymed.nlm.nih.gov. Read October 3, 2026.

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