Skin pigmentation, sexual health, appetite suppression
Not approved; clinical development discontinued
1990s · University of Arizona
SC injection (primary), intranasal, sublingual
Overview
Melanotan II (MT-II) was developed in the 1990s by researchers at the University of Arizona (including MacEwen, Hruby, and Dorr) as a highly stable, "superpotent" cyclic analog of the naturally occurring alpha-melanocyte-stimulating hormone (α-MSH) [1]. The original goal was to create a peptide capable of inducing melanogenesis (skin darkening) without UV exposure, with the intent of developing a prophylactic treatment against skin cancer.
Early Phase I trials delivered an unexpected finding: beyond tanning, MT-II produced robust pro-erectile and libido-enhancing effects. Subsequent Phase II trials formally confirmed these effects, generating significant research interest in the compound as a potential treatment for erectile dysfunction [1][2].
Clinical development was ultimately abandoned due to a non-selective receptor binding profile that produced severe and unacceptable side effects. Researchers subsequently developed Bremelanotide (PT-141), a more selective analog, which achieved FDA approval in 2019 as Vyleesi for hypoactive sexual desire disorder in premenopausal women [4].
Mechanism of Action
MT-II is a synthetic cyclic heptapeptide that functions as a non-selective agonist at four melanocortin receptor subtypes (MC1R, MC3R, MC4R, MC5R). This broad receptor activity drives both its intended effects and its problematic side effect profile.
-
MC1R (skin): Stimulates melanocytes to produce eumelanin, causing progressive skin darkening without UV exposure [1].
-
MC3R / MC4R (hypothalamus): Triggers pro-erectile signaling via nitric oxide (NO) pathways, increases sexual desire, and exerts anorexigenic (appetite-suppressing) effects [4][5].
-
Non-selectivity: Because MT-II engages all four receptor subtypes rather than targeting a specific one, it cannot produce its desired effects without simultaneously triggering widespread systemic responses: nausea, cardiovascular effects, spontaneous erections, and more.
Clinical Trials
MT-II progressed through Phase I and Phase II human trials between 1996 and 2000, producing some of the most striking efficacy results seen in erectile dysfunction research at the time. Development was not halted for lack of effect; it was halted because the side effects were deemed unacceptable for mainstream clinical use.
| Study & Year | Design & Subjects | Route / Dose | Key Outcome | Ref |
|---|---|---|---|---|
|
Phase I pilot study 1996 |
Healthy adult men · 3 alternating daily doses | SC | Safely induced skin pigmentation. Unexpectedly revealed intense pro-erectile activity, nausea, and yawning as primary side effects. | [1] |
|
Phase II: psychogenic ED 1998 · Double-blind crossover |
10 men with psychogenic erectile dysfunction | SC · 0.025 mg/kg | 8 of 10 men achieved clinically apparent erections. Mean rigidity duration 38 min vs. 3 min for placebo. | [2] |
|
Phase II: organic ED 2000 · Single-dose crossover |
19 men with organic erectile dysfunction | SC · 0.025 mg/kg | Erections initiated in 12 of 19 active doses vs. 1 of 21 placebo doses. Sexual desire significantly elevated vs. placebo. | [3] |
|
Phase II: erection & desire 2000 · Single dose |
20 men (organic and psychogenic ED) | SC · Single dose | Erection in 17 of 20 subjects without visual sexual stimulation. Increased desire in 68% of MT-II doses vs. 19% placebo. | [4] |
Why development stopped: Despite strong efficacy signals, trials were discontinued due to unacceptable rates of severe nausea, yawning/stretching, cardiovascular strain, and unwanted spontaneous erections. The successor compound Bremelanotide (PT-141), a more receptor-selective analog, later achieved FDA approval as Vyleesi in 2019.
Dosing & Administration
No standardized, FDA-approved dosing schedule exists. MT-II was never approved for human use. The patterns below reflect what appeared in peer-reviewed clinical trials and are documented here for reference only.
- Phase I/II clinical trials (ED): Single subcutaneous injection at 0.025 mg/kg (~1.75 mg for a 70 kg subject).
- Wellness/cosmetic clinic pattern (tanning): Microdoses of 100–250 mcg SC daily to build pigmentation, followed by maintenance doses once or twice weekly.
- Primary route (clinical trials): Subcutaneous (SC) injection, the only route established in peer-reviewed clinical data.
- Other routes: Intranasal and sublingual tablet formulations are compounded and sold by research vendors; these routes lack controlled clinical validation.
Safety Risks & Regulatory Status
Documented Safety Risks of Unregulated Use
- Sympathomimetic excess: Dangerous spikes in blood pressure, tachycardia, diaphoresis, and severe anxiety have been documented from impure synthesis or incorrect dosing [6].
- Rhabdomyolysis: Life-threatening muscle breakdown releasing myoglobin, potentially causing acute renal failure [6].
- Dermatological dangers: Rapid darkening of existing moles, eruption of atypical (dysplastic) nevi, and a documented association with increased melanoma risk [7].
- Systemic toxicity: From impure synthesis, contaminants, or uncontrolled dosing (a significant risk given the entirely unregulated supply chain).
- FDA Status: Not approved. Melanotan II was never granted FDA approval. Clinical development was formally discontinued after Phase II trials.
- Bremelanotide (PT-141 / Vyleesi): The selective follow-on compound developed from MT-II research received FDA approval in 2019 for hypoactive sexual desire disorder. It is the only melanocortin-pathway drug currently approved for human use.
Market Overview
Please note: The following data is based on February 2026 pricing from vendors listed on Finnrick Analytics. All products are strictly sold as research chemicals. Prices fluctuate based on volume, batch, purity, and presentation.
SC Injectable
Lyophilized- Price range: $3.00 – $6.20 / mg
- Typical size: 10 mg vials
- Vendors with pricing: 8 of 17 surveyed
Nasal Spray
100 mcg/spray- Price: ~$10.39 / mg
- Typical size: 10 mg bottle
- Note: Lacks clinical validation for this route
Sublingual Tablets
200 mcg / tab- Price range: $7.32 – $7.89 / mg
- Sizes: 4 mg, 8 mg, 12 mg
- Note: Lacks clinical validation for this route
Vendor Directory
Vendor list sourced from Finnrick Analytics – Melanotan II page. Data collected February 2026. Tables are split by formulation; vendors without public pricing are listed separately below.
SC Injection: Lyophilized Powder
| Vendor | Size (mg) | Price (USD) | $/mg | Website |
|---|---|---|---|---|
| Nuscience Peptides | 10 | $29.99 * | $3.00 | nusciencepeptides.com |
| Planet Peptide | 10 | $30.00 * | $3.00 | planetpeptide.com |
| Amino Amigos | 10 | $40.00 | $4.00 | aminoamigos.com |
| Elite Research USA | 10 | $42.00 | $4.20 | eliteresearchusa.com |
| Uther | 10 | $43.00 | $4.30 | utherpeptide.com |
| Eternal Peptides | 10 | $54.99 * | $5.50 | eternalpeptides.com |
| Pure Rawz | 10 | $57.39 | $5.74 | purerawz.co |
| HK Peptides | 10 | $62.00 * | $6.20 | hkpeptidesworldwide.com |
| Deuschem | 10 | €31.00 | EUR pricing | deuschem.com |
Nasal Spray
| Vendor | Size (mg) | Price (USD) | $/mg | Website |
|---|---|---|---|---|
| Pure Rawz | 10 | $103.85 | $10.39 | purerawz.co |
Sublingual Tablets (200 mcg / tablet)
| Vendor | Size (mg) | Tablets | Price (USD) | $/mg | Website |
|---|---|---|---|---|---|
| Pure Rawz | 4 | 20 | $31.55 | $7.89 | purerawz.co |
| Pure Rawz | 8 | 40 | $58.52 | $7.32 | purerawz.co |
| Pure Rawz | 12 | 60 | $94.68 | $7.89 | purerawz.co |
No Public Pricing
These vendors carry or have carried Melanotan II but do not list public retail prices, require login, or are temporarily unavailable.
| Vendor | Status | Website |
|---|---|---|
| Injectify | Account registration required to view catalog | injectify.com |
| Atomik Labz | Login required to view catalog and pricing | atomiclabz.com |
| Bulk Peptide Supply | Login required to view catalog and pricing | bulkpeptidesupply.com |
| Verified Peptides | Melanotan II not currently listed | verifiedpeptides.com |
| PeptiLab Research | Melanotan II discontinued; only Melanotan I listed | peptilab.com |
| Skye Peptides | 404 on MT-II page; login required per prior research | skyepeptides.com |
| Suaway Lab Research | Site temporarily closed for facility expansion (as of Feb 2026) | suawaylab.com |
| Xingruida XDR | B2B/wholesale only; inquiry-based (Chinese manufacturer) | xingruida.com |
* Data Notes: Data collected February 2026. All products sold strictly for in-vitro research purposes. Prices subject to change. * Sale price active at time of data collection; verify current pricing before purchasing.
References
- Dorr RT, et al. "Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study." Life Sciences (1996). [PMID: 8637402]
- Wessells H, et al. "Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction: double-blind, placebo controlled crossover study." Journal of Urology (1998). [PMID: 9679884]
- Wessells H, et al. "Effect of an alpha-melanocyte stimulating hormone analog on penile erection and sexual desire in men with organic erectile dysfunction." Urology (2000). [PMID: 11018622]
- Molinoff PB, et al. "Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II." International Journal of Impotence Research (2000). [PMID: 11035391]
- Cone RD. "Anatomy and regulation of the central melanocortin system." Nature Neuroscience (2005). [Review of MC3R/MC4R pathways]
- Loughnan G, et al. "Melanotan II and the risk of rhabdomyolysis and sympathomimetic excess: case reports and safety review." Clinical Toxicology (2018).
- Hamill M, et al. "Melanoma associated with use of Melanotan-II." Australasian Journal of Dermatology (2013).