Melanotan II
The unapproved 'tanning peptide' that PT-141 was spun off from. It carries a real mole and skin-monitoring caveat worth surfacing.
What is Melanotan II?
Melanotan II (MT-2) is the compound PT-141 was derived from. It is a synthetic, non-selective melanocortin agonist first researched as a way to trigger tanning without sun exposure. During that research, a striking libido side effect showed up, and that observation is literally what led to the development of PT-141. MT-2 itself never made it to approval, and it is worth being clear-eyed about why: its lack of receptor selectivity is both the source of its effects and the source of its problems.
How Melanotan II works
Where PT-141 is relatively focused, MT-2 activates melanocortin receptors broadly, hitting MC1R, MC3R, MC4R, and MC5R. Each does something different. MC1R drives melanin production, which is the tanning effect. MC4R in the hypothalamus drives the sexual-arousal and appetite effects. MC5R influences the oil glands. Because it stimulates all of them at once, you cannot really get the tan without also getting the other systemic effects, and that lack of selectivity is exactly what makes it hard to control.
What the research shows
The tanning and libido effects are real and reproducible: users typically see pigmentation build over several weeks, and pro-erectile and arousal effects are well documented. But high-quality, long-term clinical data on MT-2 specifically is limited, and it was never approved precisely because the side-effect profile was too broad for regulators. Critically, a darker tan from MT-2 does not protect against UV damage, so it is not a safe substitute for sunscreen. This is a case where the mechanism clearly "works" but the risk-to-benefit ratio is why it stalled.
Dosage and how it is used
There is no approved dose, and MT-2 is essentially always obtained through unregulated channels, which means purity and concentration are uncertain. Community tanning protocols use small subcutaneous doses with a "loading" then "maintenance" pattern, but none of this is clinically validated, and the uncertain sourcing compounds the risk. This is one of the less controllable compounds in this library.
→ How to reconstitute Melanotan II: calculator, units to draw & storage
Side effects and safety
Nausea and facial flushing are very common, especially early on, and spontaneous erections and appetite suppression are frequently reported due to MC4R activity. More serious concerns include transient blood-pressure and heart-rate changes and case reports of priapism (a prolonged, painful erection that is a medical emergency). The one that dermatologists flag most is the skin: MT-2 can darken existing moles and prompt new ones, which makes monitoring for melanoma genuinely important. New or changing moles while using it warrant a dermatologist's evaluation.
- Research depth: moderate; limited high-quality long-term human data.
- Darkens and can change moles; melanoma monitoring is a real, specific concern.
- Not FDA-approved, almost always from unregulated sources. Verify status independently.
Frequently asked questions
How is Melanotan II related to PT-141?
PT-141 (bremelanotide) was developed out of Melanotan II research. MT-2's libido side effect during tanning studies pointed researchers toward a more focused melanocortin compound, which became the FDA-approved PT-141. MT-2 itself is the broader, less selective, unapproved parent.
Does Melanotan II protect against sunburn?
No. The tan it produces does not provide meaningful UV protection, and sun exposure still causes DNA damage. It is not a substitute for sunscreen, and treating it as one is a real risk.
Is Melanotan II dangerous for moles or skin cancer?
It can darken existing moles and prompt new ones, which is why dermatologists flag melanoma monitoring as important. Any new or changing mole while using it should be evaluated by a dermatologist.
Is Melanotan II FDA-approved?
No. It never gained approval, largely because its broad, non-selective mechanism produced too many side effects. It is almost always sourced from unregulated suppliers, adding purity and dosing risk.
References
Track Melanotan II in Peptide AI
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Download the appEducational information only. This is not medical advice. Peptide AI is an informational and tracking platform. Everything on this page is for general education. It is not a substitute for professional medical advice and is not a recommendation to use any compound. Many peptides listed here are research compounds the FDA has not approved for human use. Talk to a qualified, licensed healthcare provider before you start, change, or stop any protocol.