Melanotan II: a non-selective melanocortin agonist, and the skin question it raises
PT-141 was derived from this molecule by narrowing it down. Melanotan II is the version that was not narrowed: it hits the whole melanocortin family, which is why it produces tanning, appetite suppression and sexual effects from one injection — and why the skin question is not optional.
Regulatory status. Research compound — not FDA approved. PT-141 (bremelanotide) is FDA approved for women's HSDD. MT-2 is a precursor compound. That is the app’s own field, reproduced here rather than summarised. It means no regulator has reviewed a manufacturer’s evidence for identity, purity, potency or safety in people for this compound, so nothing below is a marketing claim about a product you can buy.
Purity, identity and concentration are therefore unverified by anyone but whoever made the vial. The storage rule in the fact box below is general practice for this formulation rather than a specification for a particular product: General handling practice for this formulation. Your supplier’s own insert or COA overrides anything here.
This page names no vendor, no clinic and no testing service, and there is no discount code anywhere on this site — the moment a page like this recommends where to buy, it stops being information.
- Also known as
- MT-2, bremelanotide precursor
- Class
- Metabolic peptide
- Regulatory status
- Research compound — not FDA approved. PT-141 (bremelanotide) is FDA approved for women's HSDD. MT-2 is a precursor compound.
- Modelled half-life
- 1 h — estimated half-life, limited human PK data
- Time to peak
- 30 min
- Formulation
- Aqueous (reconstituted powder)
- Before mixing
- Sealed powder tolerates room temperature in transit, but keep it refrigerated at 2–8 °C (36–46 °F) for anything beyond a few weeks, or frozen for months. Keep it dark — the carton it shipped in is doing a job.
- After mixing
- Once reconstituted with bacteriostatic water: refrigerate at 2–8 °C and use within about 28 days. The benzyl alcohol in bacteriostatic water is what buys that window — plain sterile water has no preservative, so a vial mixed with it should be treated as one sitting only. Kits are usually ten vials: only the one you mixed is on that 28-day clock — the sealed ones keep their own, much longer shelf life, so store them as powder, not as solution.
- What ruins it
- Do not freeze a reconstituted vial. Repeated freeze–thaw is one of the more reliable ways to degrade a peptide.
- Handling caveat
- General handling practice for this formulation. Your supplier’s own insert or COA overrides anything here.
One peptide, four receptors
Established clinical use Alpha-melanocyte stimulating hormone acts across a family of receptors with quite different jobs. MC1R on melanocytes controls melanin production. MC3R and MC4R in the hypothalamus are involved in energy balance, appetite and sexual arousal. MC5R sits in exocrine tissue including sebaceous glands. Melanotan II is a cyclic analogue that activates all of them without much selectivity.
That explains the whole effect profile in one sentence. Tanning without ultraviolet exposure is MC1R. Reduced appetite is MC3R and MC4R. Spontaneous erections and increased desire are MC4R — the same mechanism PT-141 uses, which is unsurprising since bremelanotide is a metabolite of this molecule. Flushing, yawning and nausea come along with the rest.
The app models its half-life at about an hour and flags it as an estimate, meaning published human pharmacokinetic data is limited or absent. That figure is the basis for the as-needed rather than daily framing in the app’s own dosing rows, and like every estimated figure on this site, anything calculated from it inherits the uncertainty.
The skin problem is the real one
Off-label or community practice Stimulating MC1R does not only produce a tan. Existing naevi darken, new pigmented lesions can appear, and the ones that were already there change appearance. Case reports of melanoma diagnosed in users exist, and what they cannot establish is causation — a compound that makes every mole on the body darker and larger is also a compound that makes an existing melanoma easier to notice, and the population using it overlaps with the population that tans deliberately.
What follows from that is practical rather than alarming. Darkening moles are the specific reason the app puts baseline photography and periodic dermatological review on the monitoring list for this compound, and it is one of the few entries in this reference where the monitoring is a skin examination rather than a blood test. Someone using this without a baseline has removed their own ability to tell a benign change from a significant one, because everything changed at once.
Anyone with a personal or family history of melanoma, a large number of atypical naevi, or previous significant sun damage is in the group where this conversation belongs with a dermatologist before rather than after.
Sourcing, and the honest comparison with the approved version
Animal-only or theoretical There is no approved product and there never has been; development was not completed. Identity, purity and concentration rest entirely with whoever made the vial, and the app’s own regulatory string says so. This site names no vendor and no testing service.
The comparison worth drawing is with PT-141, which is the MC4R-selective fragment and which does have an approval, for one indication in one population. If the reason for interest is sexual function, the approved molecule targets that receptor specifically and leaves MC1R largely alone — which removes the skin question rather than managing it. If the reason for interest is tanning, there is no approved option, and the honest framing is that the trade is a cosmetic effect against an unquantified dermatological risk.
Nausea and transient blood pressure changes are the common effects, and dose titration from very low is what the app’s rows describe for that reason. Anything here belongs with a clinician who knows your history — dermatological history included — rather than being worked out from a page.
How long one dose lasts
pkCurve function.
The vertical axis is relative: the shape carries across people, the absolute
concentration does not. This compound’s half-life is flagged as an estimate in the app, so read the curve as the right shape rather than the right numbers.Try other intervals on the half-life and steady-state calculator, which runs the same function against whatever cadence you type.
The dosing rows the app records
Animal-only or theoretical Reproduced from the app’s reference so you can see what it holds, not as a recommendation. Which row applies to a particular person, if any, is a clinical decision this page does not make — and rows describing supraphysiological or post-cycle use are filtered out before this table is built, so what you see here is a subset.
| Label | Amount | Route and frequency | Duration recorded |
|---|---|---|---|
| Starting (tanning) | 0.25mg | SubQ before tanning/bedtime | Build up slowly |
| Standard | 0.5-1mg | SubQ as needed — not daily use | Cycle on/off |
| Sexual function | 0.5-1mg | SubQ 30-60 min before activity | As needed |
What the app monitors alongside it
The panel below is the app’s own monitoring note for Melanotan II, verbatim. None of the analytes it names has a page here yet.
- Monitoring panel
- Skin monitoring — photograph moles at baseline and every 3 months. Blood pressure (transient elevation). Dermatologist consultation before long-term use.
Drawbacks and risks the app records
From the app’s own entry. The mole item is not a cosmetic footnote; it is the one that changes what monitoring this compound needs.
- Nausea — most common side effect, dose-dependent
- Facial flushing
- Spontaneous erections can be problematic
- Moles and nevi can darken — skin check important
- Yawning and drowsiness at higher doses
- Not FDA approved — PT-141 (bremelanotide) is the FDA-approved version for women
Interaction rules that name Melanotan II
From the app’s interaction data, filtered so no rule naming a compound this site does not publish appears. Not exhaustive, and not a safety clearance: a combination that is not listed is one nobody has documented here, which is not the same as one that is fine. The combination checker has the rest.
MT-2 and PT-141 — Overlap in Mechanism
MT-2 and PT-141 (bremelanotide) both activate MC4R for sexual function enhancement. They overlap significantly in mechanism. Using both simultaneously provides little additional benefit and increases side effect risk (nausea, flushing, blood pressure elevation). Use one at a time.
What to watch: Blood pressure (both cause transient elevation), nausea assessment.
MT-2 + TRT — Monitor Skin and E2
MT-2 can darken existing moles and nevi. On TRT, where estrogen can also affect skin, monitoring skin changes is important. E2 optimization is also important as both estrogen and melanocortin pathways affect libido — don't over-suppress E2 if also using MT-2 for sexual function.
What to watch: Dermatology skin check baseline and every 6 months. E2 (sensitive assay) — maintain 20-35 pg/mL for optimal libido synergy.
Questions people actually ask
How is it different from PT-141?
PT-141 is bremelanotide, a metabolite of this molecule, and it is far more selective for MC4R. That means it produces the sexual effect without much of the pigmentation effect — and it has an approval, which MT-2 does not.
Does the tan protect against sunburn?
Melanin produced this way is real melanin, but treating it as sun protection is not supported and the practice it is usually paired with — using it alongside deliberate ultraviolet exposure to "start" the tan — adds the exposure risk back on top. It does not replace sunscreen.
What monitoring does it actually need?
A skin examination, which is unusual for this reference. Baseline photography of existing moles and periodic dermatological review, because the compound changes the appearance of every pigmented lesion at once and removes the usual signal.
Why the spontaneous erections?
MC4R activation in the hypothalamus, the same mechanism the approved fragment uses deliberately. In a non-selective agonist it arrives whether or not that was the reason for taking it, and the app’s drawbacks list flags it as a practical problem rather than a benefit.
Where the load-bearing numbers come from
Named rather than linked. Publisher URLs move, and a citation that resolves to a 404 two years from now is worse than one you can search for by name — every entry below is findable from the title and year alone.
- Melanocortin receptor subtypes and their functions
- Standard endocrinology and dermatology references on the melanocortin system
- Bremelanotide as a metabolite of melanotan II
- The published development history of both molecules
- Pigmented lesion change and melanoma case reports
- Dermatology case reports and series; causation is not established
- Estimated half-life
- app.html’s TL_PK entry, flagged est: limited or absent human pharmacokinetic data
Baseline photographs and dated doses are the whole monitoring plan for this one. TherapyLog keeps the dates.
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