Melanotan II

Melanotan II is a synthetic cyclic peptide modeled on alpha-melanocyte-stimulating hormone (alpha-MSH), the natural signal that drives skin pigmentation ¹⁸. It activates a family of melanocortin receptors, with broader activity at MC4R than the related tanning peptide melanotan I, which gives it appetite and sexual effects in addition to tanning ⁵.

The first human evaluation was a 1996 pilot Phase I study ¹. Spontaneous erections during early testing led to small studies in men with erectile dysfunction ², but no approved product followed. Today the compound is sold online as an unregulated injectable, nasal spray, or powder ⁶, and Australia's TGA has warned against its use ⁸.

Studied areas:

• Tanning and skin darkening: strong effect in user reports, with all 28 users in one series reporting darker skin ⁶.
• Sexual function: pro-erectile effects in small human studies ².
• Appetite and metabolism: robust animal data, but no human trials confirm long-term use ²¹.
• Other areas: alcohol intake, nerve repair, and melanoma biology have only preclinical evidence ⁴⁰.

Melanotan II works by mimicking melanocortin signaling. It docks onto melanocortin receptors, switches that control pigment, appetite, metabolism, and sexual response ⁴.

Primary pathways

• MC1R in skin: activation raises tyrosinase activity and eumelanin production, leading to skin and mucosal pigmentation without UV exposure ¹. Oral pigmentation has been observed in a case report ⁹.
• MC4R in the brain: appetite suppression appears to require beta-arrestin 2 signaling downstream of MC4R ²⁵. Animal studies show reduced food intake and body fat ²¹.
• MC3R/MC4R in feeding circuitry: Melanotan II changes inhibitory tone in hypothalamic neurons involved in energy balance ²⁶.

Secondary actions

Animal research also reports increased brown-fat thermogenesis ²¹, improved insulin sensitivity ³¹, pro-erectile effects ³⁴, and a blood-pressure increase with chronic central activation ³⁹. The compound clears quickly from plasma and has low brain penetration relative to plasma in rodents, but systemic dosing still produces documented central effects ¹⁶.

Most human data are observational rather than trial-grade.

• Skin darkening: universal in a 28-person user series, with or without deliberate UV ⁶.
• Nevus changes: darkening of existing moles and eruptive nevi can appear within 24 hours of one injection ²².
• Nausea and flushing: the most common user-reported side effects ⁶.
• Increased libido and erections: documented in men with organic erectile dysfunction ²; priapism is a rare but serious event ¹¹.
• Appetite suppression: clear in diet-induced obese rats, where six days of central infusion reduced body weight, visceral fat, insulin, and cholesterol ²¹. Human appetite data are uncontrolled ⁶.
• Pigment changes can persist: buccal pigmentation faded within a month after stopping in one case, while gingival pigmentation was still visible at three months ⁹.

Early human clinical work used acute weight-based subcutaneous dosing, around 25 mcg/kg (practitioner consensus) in erectile-function studies ². For tanning, no validated human dose exists. The pattern that appears repeatedly in qualitative user research is a short daily loading phase, followed by a lower-frequency maintenance phase ⁶.

Real-world courses vary from a single injection to 64 days of self-administration ⁹. Community protocols often pair doses with deliberate UV or sunbed exposure, although pigmentation occurs without UV ⁶. Evening dosing is a community convention, partly to sleep through early nausea, and no human chronopharmacology evidence exists. In rodents, time of day affects some metabolic outcomes ⁴⁴.

Route data:

• Subcutaneous: the dominant human route in user reports ⁶.
• Intranasal: sprays are marketed ⁷, but rat data suggest weaker central exposure by this route ³⁵.
• Topical: experimental for melanoma in mice, not a human tanning route ³⁸.
• Oral: absent from reported protocols.

Melanotan II is distributed as a freeze-dried powder and is typically reconstituted with bacteriostatic water ⁶. Independent analysis found that vials labeled 10 mg contained only 4.32 to 8.84 mg of actual peptide, with 4.1 to 5.9 percent impurities in two of three products tested ¹⁴. Treat label mass as approximate.

Handling guidance in the research materials is to add diluent slowly down the vial wall and swirl gently, without shaking. U-100 insulin syringes are the standard for research volumes. Reconstituted solution should be kept at 2 to 8°C and discarded after roughly 30 days; do not freeze after reconstitution. Lyophilized powder can be held at 2 to 8°C short term or at −20°C long term. Use the calculator in this section to convert a selected dose into a volume for the vial and diluent chosen.

Formal human drug-interaction studies do not exist; the human clinical literature is limited to early pilot and small erectile-function studies ¹.

• PDE5 inhibitors and other erectile agents: additive priapism risk. Ischemic priapism has been reported with Melanotan II alone ¹¹, and its pro-erectile pathway overlaps with apomorphine and oxytocin ³⁴.
• Sunbeds and UV: melanoma cases co-occur with tanning-bed use ¹⁰. This is the dominant real-world interaction risk.
• Melanocortin antagonists: AgRP-derived blockers oppose central effects in animal models ⁴⁸.
• Naltrexone: synergistic reduction of binge-like alcohol intake in mice ⁴⁹.
• Serotonergic and incretin anorectics: theoretical additive appetite suppression through shared brainstem circuits ⁵⁰.
• Blood-pressure context: chronic central MC3/4 activation raised blood pressure in rats, and impaired nitric-oxide signaling amplified it ³⁹.

No controlled trial has defined a Melanotan II cycle. The common community pattern is a loading phase, followed by lower-frequency maintenance and an off period ⁶. Continuous use is also reported, including a 64-day course ⁹.

The logic for cycling in the literature is practical rather than pharmacologically validated:

• Pigment output saturates, and skin color persists for weeks after stopping ⁶.
• Nausea and sexual side effects accumulate with continued dosing ⁶.
• Breaks allow new or changing moles to be reassessed ²².
• Product variability makes stable long-term dosing unreliable ¹⁴.

Cases that prompted breaks include eruptive or changing nevi ²², prolonged erections beyond four hours ¹¹, renal infarction ¹², rhabdomyolysis ¹³, and persistent oral pigment ⁹. No withdrawal syndrome is documented.

No controlled human stacking studies exist. In seized black-market products, Melanotan II has been found alongside growth-hormone-axis and healing peptides ⁵², which confirms co-use is common but not that it is safe.

• GLP-1 receptor agonists: animal circuit data suggest additive appetite suppression and nausea are plausible ⁵⁰.
• Bremelanotide (PT-141): a related melanocortin drug that acts at the same receptor family, so stacking duplicates mechanism and risk ⁵.
• Melanotan I: overlapping pigmentation action makes the combination redundant ⁵.
• Naltrexone: positive synergy for reducing alcohol intake in mice ⁴⁹.
• Stimulants and thermogenic agents: chronic melanocortin activation raises blood pressure in animals ³⁹, and rhabdomyolysis has occurred with Melanotan II alone ¹³.

Melanotan II is not FDA approved for any indication and is sold as an unregulated research peptide ⁶. Australia's TGA has warned against its use ⁸, and Australian dermatologists have described unregulated use as a public-health interest ⁵⁵. It is not listed by the DEA as a controlled substance in the US, although it sits in a gray-market supply chain with poor purity control ¹⁴.

In the UK it is unlicensed and promoted as the 'Barbie drug' or 'vacation peptide' ⁵. EU forensic toxicology classifies it as not legally marketed, recovered in black-market performance and image enhancing drug seizures ⁵². No WADA-specific schedule is documented in the available sources, but the compound appears among performance and image enhancing drugs ⁵².

A related melanocortin drug, bremelanotide (PT-141), later received FDA approval for low sexual desire, but that approval does not extend to Melanotan II ²⁴.

Safety evidence is dominated by case reports and qualitative user studies, not controlled trials ⁶. The most common reported effects are dose-dependent nausea, facial flushing, and loss of appetite ⁶. Skin and mole changes are frequent: generalized darkening, darkening or enlargement of existing moles, eruptive nevi, and oral mucosal pigmentation have all been documented ⁹.

Serious events reported in the literature include:

• Cutaneous melanoma and melanoma in situ ¹⁰
• Ischemic priapism, including after overdose ¹¹
• Renal infarction ¹²
• Systemic toxicity with rhabdomyolysis ¹³
• Melanoma-prone groups: users with a personal or family history of melanoma or atypical mole syndrome (FAMMM) should avoid Melanotan II, since a case report documents severe nevus changes in a FAMMM-affected teenage user after injections and sunbed use.

Because vials are unregulated, under-filled and impure product further confuses risk assessment ¹⁴. Baseline and interval skin exams with dermoscopy are emphasized in monitoring guidance for changing moles ²², and UV co-exposure is a common factor in melanoma case reports ¹⁰.