Melanotan II
Non-selective melanocortin receptor agonist
A cyclic alpha-MSH analog studied for melanogenesis and, through MC4R activity, libido and appetite effects.
How it works
Melanotan II (CAS 121062-08-6) is a cyclic, truncated analog of alpha-melanocyte-stimulating hormone. Unlike Melanotan I, which is comparatively selective for MC1R, Melanotan II is non-selective and binds MC1R, MC3R, MC4R and MC5R. That breadth is the defining feature of the compound in the literature and the reason it is used as a reference agonist for the melanocortin system as a whole.
MC1R activation on melanocytes drives eumelanin synthesis, which is the pigmentation endpoint most often measured. The cyclic lactam bridge in the molecule confers resistance to enzymatic degradation, giving it a far longer duration of action than native alpha-MSH.
MC3R and MC4R sit largely in the central nervous system, where they participate in energy balance and sexual arousal signaling. Central MC4R activity is what separates Melanotan II from Melanotan I in reported outcomes, and it is the pathway that the later derivative PT-141 was developed to isolate.
Reported effects in the literature cluster into pigmentation, appetite suppression and arousal responses, alongside commonly reported nausea, flushing and spontaneous darkening of existing nevi. Melanocytic lesion monitoring is emphasized throughout the published work because the compound acts directly on melanocyte activity.
What research has shown
Studies report dose-dependent tanning with lower UV exposure, plus MC4R-mediated erectile response, nausea and flushing.
Reported ranges in the literature
Low end
100 mcg daily during loading
Optimal
250 to 500 mcg daily during loading, then 1 to 2 times weekly
High end
1 mg per administration in research reports
Frequency reported in the literature: Daily loading then weekly maintenance in reported protocols. Note: Non-selective receptor activity is why side effects are broader than with Melanotan I.
Protocol duration and pairing
Typical study duration
10 to 30 day loading followed by maintenance.
Best paired with
Shares the melanocortin pathway with PT-141, which is a derivative of it.
Frequently asked questions
What is Melanotan II?
Melanotan II is a non-selective melanocortin receptor agonist, CAS 121062-08-6, used as a reference compound for MC1R, MC3R and MC4R activity in melanocortin research.
How does Melanotan II differ from Melanotan I?
Melanotan I is comparatively selective for MC1R and is studied mainly for pigmentation and photoprotection. Melanotan II also engages the central MC3R and MC4R receptors, which is why appetite and arousal endpoints appear in its literature and not in Melanotan I work.
How does it relate to PT-141?
PT-141, bremelanotide, is a metabolite and derivative of Melanotan II developed to isolate MC4R arousal signaling while reducing the pigmentation activity that comes from MC1R.
What does the research show?
Studies report dose-dependent increases in pigmentation with reduced ultraviolet exposure, MC4R mediated erectile response, and reduced food intake, along with nausea and flushing as the most frequently reported effects.
What monitoring does the literature emphasize?
Melanocytic lesion monitoring, because the compound directly stimulates melanocyte activity and darkening of existing nevi is commonly reported.
How long are research blocks typically?
Reported protocols use a 10 to 30 day loading period followed by less frequent maintenance administration.
Related compounds
Further reading
Research use only
All content on this page is general reference information for laboratory research contexts. It is not medical advice, is not intended to direct human use, and does not replace guidance from a licensed healthcare professional. Not for human consumption. Must be 18+.