Melanotan II
A synthetic cyclic analogue of α-melanocyte-stimulating hormone investigated for melanocortin-receptor activation, melanin production, pigmentation, appetite signalling and centrally mediated behavioural responses.
This selector presents the PHONYX research format and must not be interpreted as a dose.
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What is Melanotan II?
Melanotan II is a synthetic cyclic peptide developed as an analogue of α-MSH, the endogenous hormone involved in melanocortin signalling. It activates several melanocortin receptors rather than acting only at the skin-associated MC1 receptor.
Research interest centres on pigmentation and melanogenesis, but the broader receptor profile also explains investigation of sexual arousal, appetite, energy balance and behavioural responses. The peptide is therefore more multifunctional—and less receptor-selective—than compounds designed for a single melanocortin pathway.
Broad melanocortin-receptor agonism
MC1R — melanogenesis
Activation of MC1R on melanocytes increases signalling associated with melanin synthesis and pigmentation following UV exposure.
MC3R / MC4R — central effects
Central melanocortin receptors are associated with appetite, energy regulation, autonomic responses and aspects of sexual behaviour.
Cyclic peptide design
The cyclic structure increases stability and receptor activity compared with the native α-MSH sequence, contributing to a broader and more persistent research profile.
Melanotan II compared with Melanotan I
| Feature | Melanotan I | Melanotan II |
|---|---|---|
| Primary receptor emphasis | More MC1R-selective | Broader MC1R, MC3R and MC4R activity |
| Main research focus | Pigmentation | Pigmentation plus central effects |
| Systemic effects | Generally narrower | More pronounced and varied |
| Predictability | More receptor-targeted | Less selective |
Melanotan II compared with PT-141
| Feature | Melanotan II | PT-141 |
|---|---|---|
| Pigmentation | Prominent MC1R-related effect | Not the principal research purpose |
| Sexual-function research | Secondary central effect | Primary development focus |
| Receptor profile | Broad melanocortin activity | More targeted central melanocortin profile |
| Research positioning | Multifunctional | Sexual-arousal focused |
Major areas of investigation
Pigmentation Melanin production and tanning response
Clinical and experimental observations describe increased pigmentation and a more rapid tanning response when melanocortin stimulation is combined with controlled UV exposure.
Photobiology Melanin and UV-related research
Increased melanin is investigated as part of the skin’s natural photoprotective response, but it does not eliminate UV-associated damage or skin-cancer risk.
Sexual behaviour Central melanocortin pathways
Research observations involving sexual arousal contributed to the later development of more targeted melanocortin compounds such as PT-141.
Appetite MC4R-associated signalling
MC4R activation is linked to appetite and energy-balance pathways, leading to research interest in appetite suppression and metabolic signalling.
Evidence limitation Unapproved research use
Melanotan II is not an approved medicinal product, and commercial research protocols should not be confused with validated clinical dosing standards.
Melanotan II research protocol formats
| Research Protocol | Dose | Frequency | Duration | Cycle Break | Research Objective |
|---|---|---|---|---|---|
| Standard Pigmentation | 0.25–1 mg | Once daily | 8–12 weeks | 4 weeks | Progressive melanocyte activation and pigmentation research |
| Libido Research | 0.5–1 mg | Every other day | 4–6 weeks | 4 weeks | Central melanocortin stimulation research |
| Metabolic Regulation | 0.25–0.5 mg | Once daily | 6–8 weeks | 4 weeks | Appetite and thermogenic pathway research |
| Maintenance Protocol | 0.25 mg | Twice weekly | Ongoing | 8 weeks | Maintenance of pigmentation after the induction phase |
Outcomes reported across melanocortin research
Pigmentation response
Increased melanocortin signalling is associated with greater melanin production and faster visible pigmentation.
Persistent colour change
Research descriptions commonly report pigmentation that persists beyond the immediate UV-exposure period.
Central behavioural effects
Sexual arousal is a documented central melanocortin effect and helped motivate PT-141 development.
MC4R-related signalling
Reduced appetite has been reported in association with central melanocortin-receptor activation.
Common observations and important warnings
Frequently reported observations include nausea—especially during initial exposure—facial or skin flushing, headache, temporary fatigue and reduced appetite. Central melanocortin activity can also produce spontaneous sexual arousal.
Darkening of freckles and melanocytic naevi is particularly important because it can complicate visual monitoring of skin lesions. Any new, changing, asymmetric, bleeding or irregularly pigmented lesion requires professional dermatological evaluation. Increased pigmentation does not make UV exposure safe.
Other reported concerns include blood-pressure changes, muscle discomfort and prolonged erections. A prolonged or painful erection is a medical emergency. Long-term safety of unapproved Melanotan II products is not established, and product identity, sterility and endotoxin burden are separate risks.
A cyclic, non-selective melanocortin analogue
Melanotan II is structurally related to α-MSH but uses a cyclic peptide design that enhances stability and receptor potency. It acts across peripheral and central melanocortin pathways rather than functioning as a selective pigmentation-only compound.
PHONYX portfolio format
Evidence behind the key claims
Frequently asked questions
What is Melanotan II?
It is a synthetic cyclic analogue of α-MSH that activates several melanocortin receptors.
Which receptor is responsible for pigmentation?
MC1R activation on melanocytes is the principal pigmentation-related pathway.
Why can it affect libido and appetite?
Melanotan II also activates central receptors such as MC3R and MC4R.
What working range is commonly described?
The provided research-oriented sources describe 250–500 mcg per application, commonly two to three times weekly for four to six weeks.
What is the maintenance phase?
Research-oriented protocols commonly describe one to two applications weekly after the target pigmentation endpoint.
How does it differ from Melanotan I?
Melanotan I is more focused on MC1R-related pigmentation, while Melanotan II has broader central and peripheral activity.
How does it differ from PT-141?
PT-141 was developed specifically for sexual-function research, while Melanotan II combines pigmentation and central melanocortin effects.
Can increased melanin replace sun protection?
No. Increased pigmentation does not eliminate UV damage, sunburn or skin-cancer risk.
Why may freckles and moles darken?
Melanocortin stimulation can increase pigment production in existing melanocytic lesions as well as surrounding skin.
Is Melanotan II an approved medicine?
No. Melanotan II is not an approved medicinal product.
Research Disclaimer
This compound is presented exclusively for laboratory and scientific research. It is not intended for human consumption, self-administration, diagnosis, treatment, cosmetic tanning, cure or prevention of disease. Information describing research protocols is provided solely for documentary and educational context and must not be interpreted as medical advice, a dosing recommendation or instructions for use. Melanotan II is not an approved medicinal product, and its clinical safety and efficacy remain unestablished.