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Melanotan II

MT-II · MT2

Melanotan II (MT-II, MT2) is a synthetic cyclic analogue of alpha-melanocyte-stimulating hormone (alpha-MSH) and a non-selective melanocortin-receptor agonist. It is sold illicitly (unlicensed, never approved) as an injectable "tanning" agent and sexual stimulant. It is not an approved medicine; the only related approved drug is afamelanotide (a different, tested peptide). The main dangers, all documented in humans, are: it darkens and can change existing moles and trigger new/atypical (dysplastic) nevi, with several reported melanomas emerging during or after use; it causes spontaneous erections and can cause ischemic priapism (a urologic emergency); and acute overdose/injection has produced sympathomimetic toxicity with severe rhabdomyolysis, acute kidney injury and renal infarction. Because it is an unregulated black-market product, injected material is frequently mislabeled, impure, or contaminated, adding infection and dosing-error risk. Long-term safety has never been established in adequate human studies. Evidence is limited to small ED trials plus case reports/series, so overall evidence quality is low.

Clinical readoutPeptide · melanocortin
Hepatic strainNone
CardiovascularNone
HPTA suppressionNone
Half-life
No adequate human…
Route
Subcutaneous injection…
Evidence
C
Active
Systemic peptide is cle…
1·t½2·t½3·t½4·t½5·t½
Illustrative single-compartment washout · each mark = one half-life · t½ ≈ No adequate human pharmacokinetic study of Melanotan II specifically has been published. Class/analogue data (Melanotan I, the closely related MT analogue given subcutaneously to human volunteers) show a rapid absorption phase (~0.07-0.79 h) and a terminal beta-phase half-life of roughly 0.8-1.7 h, i.e. short (hours). MT-II half-life in humans is not established.
Pharmacology

Mechanism of action

Melanotan II is a cyclic lactam heptapeptide analogue of alpha-MSH that acts as a potent, non-selective agonist at melanocortin receptors (MC1R, MC3R, MC4R, MC5R). MC1R agonism on cutaneous melanocytes stimulates eumelanin synthesis (melanogenesis), producing skin darkening independent of, but potentiated by, UV exposure. Central MC3R/MC4R agonism in the hypothalamus/CNS mediates its non-genital-stimulus (spontaneous) erectogenic effect, increased sexual desire, appetite suppression, and side effects such as yawning and nausea. It is more metabolically stable and longer-acting than native alpha-MSH. It has no androgenic or anabolic-steroid activity and does not act on the hypothalamic-pituitary-gonadal axis through sex-steroid pathways.
Kinetics

Pharmacokinetics

Half-life

No adequate human pharmacokinetic study of Melanotan II specifically has been published. Class/analogue data (Melanotan I, the closely related MT analogue given subcutaneously to human volunteers) show a rapid absorption phase (~0.07-0.79 h) and a terminal beta-phase half-life of roughly 0.8-1.7 h, i.e. short (hours). MT-II half-life in humans is not established.

Active duration

Systemic peptide is cleared within hours, but the biological (tanning) effect is markedly delayed and prolonged: for the analogue MT-I, pigmentation peaked ~1 week after dosing and persisted ~3 weeks after a 10-dose course, reflecting downstream melanogenesis rather than drug persistence. Erectogenic effects in MT-II trials occurred within 1-6 h of a dose.

Route

Subcutaneous injection is the route used both in human trials and in illicit use; the analogue MT-I was essentially fully bioavailable subcutaneously and undetectable after oral dosing (peptide is not orally bioavailable). Intranasal use is also reported illicitly but is not characterized.

Metabolism & clearance

Cleared as a peptide (proteolytic degradation) with minimal renal excretion of parent drug; for the analogue MT-I <4% of dose was recovered unchanged in urine and plasma clearance was ~0.12-0.19 L/kg/h. MT-II-specific clearance in humans is not established; the pharmacokinetic figures given here are for monitoring/washout context only and are extrapolated largely from the analogue and preclinical data.

For monitoring and washout planning, not drug-test evasion.

Reported effects

Physiological & performance effects

  • Skin darkening/tanning via increased melanogenesis (the primary reason for illicit use)
  • Spontaneous penile erection without sexual stimulation and increased sexual desire (documented in small ED trials)
  • Appetite suppression / decreased food intake
  • Darkening, enlargement and increased number of melanocytic nevi (moles); new and atypical/dysplastic nevi
  • Facial flushing
  • Yawning and stretching
Safety

Adverse effects by system

Cardiovascular

Acute sympathomimetic-type toxicity has been reported after injection, including tachycardia (heart rate up to ~146 bpm), hypertension, diaphoresis and tremor in a documented overdose/systemic-toxicity case. A case of renal infarction raises concern for a thrombotic/vasospastic vascular effect. No controlled human cardiovascular safety data exist.

Hepatic

No established hepatotoxicity and no adequate human liver-outcome data. Melanotan II is a peptide with no known structural liver toxicity and drug-induced liver injury has not been a reported feature; liver effects are essentially uncharacterized.

Endocrine / HPTA

As a melanocortin agonist it has central endocrine/appetite effects (appetite suppression, yawning, nausea) but no evidence of hypothalamic-pituitary-gonadal (sex-hormone) axis suppression; it is not androgenic/anabolic. Effects on other endocrine axes in humans are not adequately studied.

Reproductive

Spontaneous erections and increased sexual desire are expected pharmacologic effects; ischemic ('low-flow') priapism, a urologic emergency requiring aspiration/irrigation and intracavernosal phenylephrine, has been reported, with erectile function not recovered at 4-week follow-up in one case. Effects on fertility are not studied.

Neuropsychiatric

No established psychiatric disorder link. Acute toxicity cases describe restlessness, anxiety and agitation as part of a sympathomimetic picture; no adequate data on mood or longer-term neuropsychiatric effects.

Renal

Acute kidney injury has been reported secondary to rhabdomyolysis after injection (rising creatinine with markedly elevated creatine kinase), and a case of renal infarction has been attributed to Melanotan II. Renal risk appears real but is documented only in case reports.

Hematologic

No direct hematologic toxicity data. The reported renal infarction raises a theoretical prothrombotic concern, but there is no adequate human evidence of a defined hematologic effect.

Dermatologic

The most consistently reported harms: generalized hyperpigmentation; darkening, enlargement and change of existing moles; eruptive/new and atypical (dysplastic) nevi; and several reported cutaneous melanomas emerging during or shortly after use (often with concurrent sunbed use). Causation with melanoma is not proven but is a repeatedly raised concern.

Recovery

HPTA suppression & recovery

Suppression: None established / not applicable by mechanism

Melanotan II is a melanocortin-receptor agonist with no androgenic or anabolic activity and no demonstrated suppression of the hypothalamic-pituitary-gonadal (sex-hormone) axis, so it is not a compound for which post-cycle HPTA recovery or SERM therapy is indicated. SERMs are not an appropriate response to Melanotan II use. Anyone with concerns about sexual, reproductive, or hormonal effects should be evaluated and managed by an endocrinologist rather than self-treating.

Bloodwork & vitals

Monitoring

Recommended labs & checks
Creatine kinase (CK) if muscle pain, weakness or dark urine after injection (rhabdomyolysis)Serum creatinine / renal function (acute kidney injury, renal infarction)Urinalysis (myoglobinuria/hematuria)Blood pressure and heart rate monitoring after dosingFull-skin examination and dermoscopy by a dermatologist, with baseline mole mapping and periodic follow-up

Cadence: Full skin/mole check by a clinician before and periodically during any use, and urgently for any changing lesion; acute labs (CK, creatinine, urinalysis) and vitals whenever systemic symptoms occur after an injection. There is no validated routine schedule because the product is unapproved.

Warning signs — seek care
  • A new, changing, enlarging, darkening, bleeding or irregular mole or pigmented lesion (possible melanoma) - seek dermatology assessment urgently
  • A painful erection lasting more than ~4 hours (priapism) - emergency care immediately
  • Muscle pain, weakness, or cola-colored urine (rhabdomyolysis)
  • Flank/abdominal pain, blood in urine, or reduced urine output (renal injury/infarction)
  • Chest pain, palpitations, severe anxiety, sweating, tremor, very high heart rate or blood pressure after injection
  • Fever, spreading redness or pus at an injection site (infection from contaminated/non-sterile product)
Do not use if

Contraindications

  • Personal or family history of melanoma or dysplastic nevus syndrome, or numerous/atypical moles
  • Concurrent UV/sunbed exposure (repeatedly associated with melanoma cases in users)
  • Any undiagnosed or changing pigmented skin lesion
  • History of priapism, sickle cell disease/trait, or other conditions predisposing to priapism
  • Personal or family history of thrombotic/vascular events (given reported renal infarction)
  • Pregnancy or breastfeeding (no safety data)
  • Use of any unregulated/black-market injectable given contamination, mislabeling and infection risk
  • Because it is unapproved and inadequately tested, there is no medically endorsed indication for non-prescription Melanotan II use
Combinations

Interaction profile

  • ModerateWith another melanocortin agonist: Additive cardiovascular strain
  • ModerateWith a thermogenic stimulant: Additive hypertension
  • ContraindicatedWith DNP: Additive cardiovascular strain

Check a specific combination in the interaction checker.

Harm reduction

Reducing harm & when to stop

  • This substance is unapproved and inadequately tested; the safest option is not to use it, and anyone considering it should discuss skin cancer and cardiovascular/urologic risk with a clinician first.
  • Have a full skin and mole examination by a dermatologist before and during any use, with baseline mole mapping; seek urgent assessment for any new, changing, darkening or irregular mole - several melanomas have been reported in users.
  • Do not combine with sunbeds or heavy UV exposure; the melanoma case reports repeatedly involve concurrent tanning-bed use, and the darkened skin can mask early lesions.
  • A painful erection lasting more than about 4 hours is a medical emergency (priapism) - go to emergency care immediately to avoid permanent erectile damage.
  • Stop and seek urgent care for muscle pain/weakness or dark urine (rhabdomyolysis), flank pain or reduced urination (kidney injury), or chest pain, palpitations, severe anxiety, sweating and very high heart rate/blood pressure after an injection.
  • Black-market vials are frequently impure, mislabeled or contaminated; there is no way to verify content or sterility, adding poisoning and infection risk on top of the drug's own effects.
  • This is not a compound where 'more' is safer or where dosing can be optimized; reported doses in the literature are attached to the harms above, not endorsed. Never share needles or reuse injection equipment.
  • Hormonal, sexual or reproductive concerns should be evaluated by an endocrinologist or urologist rather than self-managed.
Evidence

Citations (16)

Every clinical claim above is tied to a primary source. Overall evidence grade C — graded to the best available evidence for its core claims.

  1. 01

    Melanotan II is a non-selective melanocortin-receptor agonist / synthetic cyclic alpha-MSH analogue used illicitly for tanning and sexual stimulation.

    Case reportPMID 31953620 ↗

  2. 02

    Melanotan II is a cyclic alpha-MSH analogue that induces skin hyperpigmentation via MC1R and is acquired unregulated online for tanning.

    ReviewPMID 34464955 ↗

  3. 03

    Melanotan II is a potent initiator of penile erection in men with psychogenic erectile dysfunction, with side effects of nausea, stretching/yawning and decreased appetite, in a double-blind placebo-controlled crossover trial.

    RCTSynthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study.PMID 9679884 ↗

  4. 04

    In men with organic erectile dysfunction, Melanotan II (0.025 mg/kg SC) initiated erections and increased sexual desire versus placebo; severe nausea occurred in 4 of 19 injections.

    RCTPMID 11018622 ↗

  5. 05

    Across human ED studies Melanotan II caused erection in 17/20 men and increased sexual desire; nausea and yawning were frequent, with 12.9% having severe nausea at 0.025 mg/kg.

    RCTPMID 11035391 ↗

  6. 06

    Subcutaneous injection of Melanotan II caused systemic sympathomimetic toxicity (tachycardia up to 146 bpm, hypertension, diaphoresis, tremor, agitation) with severe rhabdomyolysis (CK to 17,773 IU/L) and acute renal dysfunction.

    Case reportMelanotan II injection resulting in systemic toxicity and rhabdomyolysisPMID 23121206 ↗

  7. 07

    Renal infarction has been attributed to Melanotan II, with possible thrombotic and direct toxic mechanisms; Melanotan II-induced rhabdomyolysis and renal failure were also reviewed.

    Case reportPMID 31953620 ↗

  8. 08

    Cutaneous melanoma occurred in a young woman after a course of Melanotan II self-injection combined with sunbed use.

    Case reportPMID 24355990 ↗

  9. 09

    Melanoma has been reported in association with melanotan use.

    Case reportPMID 21564053 ↗

  10. 10

    Melanotan use is associated with melanocytic changes in existing moles and new/dysplastic nevi, and four case reports describe melanomas emerging from existing moles during or shortly after melanotan use; national health bodies have issued safety warnings.

    ReviewPMID 28266027 ↗

  11. 11

    Melanotan is a recognized trigger of eruptive melanocytic nevi (sudden onset of multiple new moles).

    ReviewPMID 31119650 ↗

  12. 12

    Acute ischemic ('low-flow') priapism requiring cavernosal aspiration, irrigation and intracavernosal phenylephrine occurred after subcutaneous melanotan injection, with erectile function not recovered at 4 weeks.

    Case reportPMID 30796078 ↗

  13. 13

    Reported user side effects and hazards include pigmented-lesion risk, infectious disease transmission, contaminated products, polypharmacy and sunbed exposure.

    Case seriesPMID 34464955 ↗

  14. 14

    For the closely related analogue melanotan-I in human volunteers, subcutaneous dosing gave a short terminal half-life (~0.8-1.7 h beta-phase), near-complete SC bioavailability, no oral bioavailability, <4% urinary recovery, and tanning that peaked ~1 week after dosing and persisted ~3 weeks.

    RCTPMID 9113347 ↗

  15. 15

    Illicit melanotan II is a falsified/unregulated black-market peptide subject to wrong active ingredient, wrong dose, absence of ingredient, and toxic contamination/impurities.

    ReviewPMID 30165334 ↗

  16. 16

    Seized illicit 'Melanotan II' samples analyzed forensically showed low purity (e.g., ~30%), confirming variable/impure black-market product.

    Case reportPMID 39302005 ↗

Last reviewed 2026-07-06 · Verified against PubMed · Educational, not medical advice