What is Melanotan 2?

What sources report

Origin and design

MT2 was developed at the University of Arizona as one of several long-acting, enzyme-resistant melanocortin analogs designed to study melanocortin receptors.⁴³ A 1994 paper described it as a cyclic heptapeptide that tans the skin and was then being evaluated for preventing sunlight-induced skin cancers.⁴⁴ Its developers later wrote that its effects on sexual function were discovered by accident during the tanning studies.⁴⁵

Skin pigmentation

The only controlled human tanning data we found come from a 1996 pilot phase 1 study in 3 healthy men.⁴⁶ Two of them had measurably darker skin on the face, upper body and buttock 1 week after the last injection, judged by reflectance measurement and by eye.² MT2 is described as acting mainly through MC1R on melanocytes, raising brown-black eumelanin independent of sun exposure.⁴⁷ We found no evidence that an MT2 tan protects against sunburn. The human sunburn data we found are for Melanotan 1, not MT2: in a 2004 study, 3 of 4 people given MT-1 tanned and had 47% fewer sunburn cells at a UV-exposed skin site.⁴⁸ The approved Melanotan 1 implant's label still tells patients to keep up sun and light protection during treatment, to prevent EPP reactions.⁴⁹ Other peptides studied for skin color are covered in Peptides and tanning.

Sexual function

In a 1998 double-blind crossover trial, 8 of 10 men with psychogenic erectile dysfunction developed clinically apparent erections after MT2.⁵⁰ In a 2000 trial in 10 men with physical risk factors, MT2 produced reported erections after 12 of 19 injections against 1 of 21 placebo doses, and desire was higher after MT2.⁵¹⁵² Across both trials, MT2 led to erections in 17 of 20 men without sexual stimulation.³ In women, the only report we found is a brief 2005 article by one of MT2's developers describing increased desire and genital arousal; its abstract gives no study size.⁵³ MT2 is not approved for any sexual problem.⁵

Appetite and weight

In rodents, MT2 given into the brain or systemically (into the body at large) sharply reduced food intake, presumably through MC4R.⁵⁴ In a 2011 rat study, MT2 infused into the brain ventricles for 10 days cut food intake by 50% to 58% over the first 6 days, in groups with and without a nitric oxide blocker, while raising blood pressure and heart rate.⁵⁵ In people, decreased appetite appeared only as a temporary side effect in one 10-man trial, and we found no human weight-loss study of MT2.⁵⁶

What the research does not cover

The MT2 research we found centers on pigmentation, sexual function and appetite. We found no study of MT2 for collagen, wrinkles, hair or skin repair; no data on how long an MT2 tan lasts or on repeated or long-term use; and, beyond the 2005 report, no data on use in women, in pregnancy or in teenagers. A 2026 review states that MT2 lacks an established human safety profile.⁵⁷ Researchers who need the compound for lab work can find Melanotan 2 for sale as a research vial.

Side effects

The three trials were small (3 to 10 men each) and gave only a few doses, too few to reveal rare or long-term effects.⁴⁶⁷ The serious harms listed below come from published case reports of people using unregulated products.¹⁴

Seen in the clinical trials

• Nausea: mild at most dose levels in the pilot study, severe after 4 of 19 injections in one trial, and severe in 12.9% of subjects at 0.025 mg/kg across both erectile dysfunction trials.²³⁵²⁴
• Stretching and yawning, often around the onset of spontaneous erections.²³⁵⁶
• Spontaneous erections without sexual stimulation, on and off for 1 to 5 hours after a dose in healthy men.²³
• Decreased appetite, more often than with placebo; it was temporary and needed no treatment.⁵⁶
• Sleepiness and fatigue (WHO grade II) in 1 of 2 men at the highest tested dose, 0.03 mg/kg.⁵⁸

Reported in case reports (frequency unknown)

• New moles and darkening of existing moles, within 24 hours of a single injection in one report and within a week of two injections in another.¹⁶⁵⁹
• Melanoma during or after use, with no proven causal link.³⁶³⁷
• Dark bands across the nails, and brown pigmentation of the gums and inner cheeks after 64 days of injections; the gum color was still visible, lighter, 3 months after stopping.¹⁷⁶⁰¹⁸
• Priapism (an erection that will not go away) needing drainage and drug injection, and surgery in one case; one man had not recovered erectile function 4 weeks later.⁶¹⁶²
• Sympathomimetic toxicity (fast heart rate, sweating, dilated pupils, tremor) followed by muscle breakdown and kidney dysfunction in a 39-year-old man after a 6 mg injection; in a 2022 report, a 27-year-old man had sympathomimetic symptoms 2 hours after injecting MT2.^12136364
• Loss of blood flow to part of a kidney (renal infarction), judged most likely caused by MT2 in a 2020 report.⁶⁵
• Posterior reversible encephalopathy syndrome (PRES), a brain condition, after melanotan use.⁶⁶
• Ulcerated wounds (pyoderma gangrenosum) at abdominal injection sites in a 65-year-old woman.⁶⁷

Warnings

• FDA says compounded Melanotan II may carry a risk of immune reactions for certain routes of administration, because of possible aggregation or peptide-related impurities.⁶⁸
• The MHRA warns that the contents of unauthorized MT2 products are unknown, and advises anyone using MT2 injections or nasal sprays to stop and to see a doctor about side effects.⁶⁹⁷⁰
• Labels and contents can differ: a Belgian forensic laboratory measured 30% purity in powder from vials labeled Melanotan II.⁸
• A 2010 review notes that the MHRA has warned about blood-borne virus transmission from shared needles and about impure products.⁷¹
• For its approved relative afamelanotide, the FDA label recommends a full body skin exam twice a year to check pigmented lesions; MT2 has no label of its own.⁷²⁵

Dosage information

No human dose of MT2 is established or approved.⁵⁵⁷ The only published trial doses come from the three small University of Arizona studies, which gave a few weight-based injections under the skin.⁴⁶⁷ A 2026 review says MT2 lacks an established human safety profile.⁵⁷ Full details: Melanotan 2 dosage.

Reconstitution and storage

Because MT2 has no FDA-approved label, there are no FDA-reviewed instructions for mixing or storing it.⁵ The supplier describes the product as a white freeze-dried solid and gives a shelf life of 36 months at -20 °C and 30 days at 2 to 8 °C, without saying whether the shorter figure covers the powder or a mixed solution.⁹ No diluent comes with the vial.⁷³ General lab steps are in the reconstitution guide, with concentration math in the reconstitution calculator.

Regulatory status

United States. FDA has not approved MT2 for any use.⁵ In 2007 it sent a warning letter to a company over the illegal sale and marketing of Melanotan II as a skin cancer preventive and tanning agent, and advised consumers using the product to stop and to consult their health care provider if they had any adverse events.⁵⁷⁴ Melanotan II was once in category 2 of FDA's interim compounding policies; its nominators withdrew the nomination, and FDA still lists its potential safety risks, including case reports of melanoma, PRES, sympathomimetic toxidrome and priapism.⁷⁵¹⁴ FDA's 503A nominations list, updated May 14, 2026, does not name it in categories 1 to 3.⁷⁶ FDA's Pharmacy Compounding Advisory Committee is due to discuss it, with LL-37, GHK-Cu, dihexa acetate and PEG-MGF, before the end of February 2027; no meeting date was posted as of October 24, 2026.⁷⁷⁷⁸ In 2020, an FDA warning letter to a Kentucky compounding pharmacy listed Melanotan II among bulk substances it had used that are not eligible for compounding under section 503A.⁸⁶

United Kingdom. The MHRA said in April 2024 that Melanotan II products are medicines if they are injectable or pens, and nasal sprays only if sold with claims to treat or prevent disease.⁷⁹⁸⁰ It says it has acted to remove melanotan products from the market for over 10 years, and it received 16 UK suspected adverse reaction reports for MT2 from 2012 to 2022.⁸¹⁸²

Elsewhere. A 2025 case report states that MT2 is unlicensed and its sale illegal in the UK and many other countries, and a 2017 review notes that multiple national health organizations have warned about melanotan I and II.⁶⁸³ In Canada, where injectable peptides are regulated as prescription drugs, Health Canada listed Melanotan II among unauthorized injectable peptides seized from or sold by an online seller in 2025, and Melanotan I and II among examples of unauthorized peptides it had seized in a 2026 advisory.⁸⁷⁸⁸

Related approved drugs. Two relatives are FDA approved: afamelanotide (Scenesse) since October 8, 2019 for adults with erythropoietic protoporphyria, and bremelanotide (Vyleesi) since June 21, 2019 for acquired, generalized hypoactive sexual desire disorder in premenopausal women.^34218442 Neither approval covers MT2. The brand profile is What is Vyleesi?.

Sport. MT2 is not named on the WADA pages our research could load or in USADA's advisory on the 2027 list, so its status is unconfirmed. USADA says that from January 1, 2027, the WADA Prohibited List names "peptides" in general in class S0 (non-approved substances), which is banned at all times, and that a peptide not named on the list may still be prohibited.¹⁰