Generic Name: Melanotan II (MT-II / MT2)
Development Code/Product Association: Originating from research at the University of Arizona, the derivative drug PT-141 (Bremelanotide) is its selective MC4R branch.
CAS Number: 121062-08-6
Molecular Weight: Approximately 1024.2 Da
Structure: Cyclic heptapeptide containing an Asp-Lys-lactam bridge (lactam) MT2 (Melanocortin) and D-Phe substitution enhance metabolic stability and affinity for MC receptors.
Appearance: White to off-white lyophilized powder
Purity: Research grade typically >=98% (HPLC verified)
Storage: Unreconstituted lyophilized powder should be stored at -20℃ protected from light and sealed (18–24 months); after reconstitution, use with antibacterial aqueous solution, refrigerate at 2–8℃, and use within 4–6 weeks. Repeated freeze-thaw cycles are strictly prohibited.
MT2 is a non-selective melanocortin receptor (Melanocortin) Receptor agonists primarily bind to MC1R, MC3R, MC4R, and MC5R, exerting their effects through the G protein-cAMP pathway:
MC1R (skin melanocytes) → activates adenylate cyclase → increases cAMP → phosphorylates CREB → upregulates tyrosinase → stimulates eumelanin (deep brown melanin) synthesis → darkens skin/hair color. It doesn't directly darken your skin; moderate UV exposure (sunlight/tanning lamps) is needed to activate existing melanin for color to appear.
MC4R (hypothalamus) → centrally enhances sexual arousal/desire (potential in both men and women); men may experience spontaneous erections (a typical pharmacological response to MC4R activation, not a side effect); simultaneously inhibits the feeding center → mild appetite suppression.
MC3R → participates in energy balance and mild anti-inflammatory regulation, a minor role.
The half-life is approximately 1-2 hours subcutaneously, but the effects of activated melanocytes can last for days to weeks, so daily injections are not necessary.
Highly Effective Tanning: Even individuals with fair skin (Fitzpatrick type I-II) can achieve a deep brown tan relatively quickly, with a significantly reduced required UV exposure time.
Long-lasting Residual Color: Activated melanocytes can maintain the tan for weeks to months, and the tan can be retained for a period after discontinuation of injections (superior to the fading speed of natural tanning).
Additional Benefits: MC4R activation leads to increased libido (spontaneous erections are more common in men) and mild appetite suppression.
No High-Dose HGH Axis Interference Required: Does not interfere with the GH-IGF1 axis, resulting in minimal disruption to the endocrine background.
Common Acute Side Effects: Facial flushing and heat (vasodilation), nausea/vomiting (dose-dependent) are common within 30 minutes after injection. These symptoms usually lessen after a few days of tolerability and can be slightly relieved by injection on an empty stomach or in the evening.
Darkening of Moles/Freckles: Existing moles, freckles, and melasma will darken and enlarge synchronously with melanocyte activation-making it impossible to distinguish between benign pigmentation changes and early melanoma changes. A history of skin cancer or a family history of melanoma is a red flag.
Potential Melanoma Controversy: While there is no confirmed direct carcinogenicity, it promotes melanocyte proliferation and induces increased UV exposure, theoretically increasing the risk of skin cancer. Dermatologists generally do not recommend it.
Special Reactions in Men: MC4R activation can cause prolonged spontaneous erections or even priapism. If it lasts more than 4 hours, emergency treatment is required.
Unapproved: There are no pharmaceutical approvals worldwide (not approved by the FDA/EMA/NMPA). It is only in research use status, and the finished product lacks regulatory protection.
Research Uses: Research on melanin receptor signaling pathways, melanin production, MC4R-mediated arousal, etc.
Caution: This is not a weight loss drug or a standard treatment. It should not be used as a substitute for sunscreen or to treat erectile dysfunction (the latter uses PT-141, which has been approved).
Absolute Contraindications: Known or suspected history of melanoma/skin cancer, active autoimmune diseases, pregnant or breastfeeding women, and individuals under 18 years of age.
Use with Caution: Numerous atypical nevi (a baseline dermatological examination and follow-up photography should be performed first), uncontrolled hypertension (MC3R/MC4R can cause transient fluctuations in heart rate and blood pressure), and a history of priapism.
Usage Reference (Research Protocol): Commonly used 10mg/vial with 2mL of antibacterial water → concentration 5mg/mL. Start with a low dose of 0.25 mg (5 units of insulin injection) subcutaneously, gradually increasing to 0.5 mg/day as a loading period (7-14 days). After reaching the target, reduce to 0.25-0.5 mg 2-3 times per week for maintenance. Inject the liquid slowly, do not shake the powder. Injecting at night may reduce nausea.
UV Coordination: After MT2 injection, moderate sun exposure or UV lamp activation is still necessary, but prolonged exposure should be avoided-the intention is to reduce UV demand, not encourage excessive sun exposure.
WADA Status: This is a prohibited substance (melanocyte-stimulating hormone mimicry), prohibited for participating athletes.
Raw Material Warning: Commercially available raw materials are all "For Research Use Only" and are unregistered. Purity varies greatly. Always request a Certificate of Analysis (COA) (HPLC+MS). The risk of microbial/endotoxin contamination from powders of unknown origin is real.
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