Melanotan I
Afamelanotide · MT-1 · MT-I · Afamelanotide · Scenesse · [Nle4, D-Phe7]-alpha-MSH · NDP-MSH
Tanning-focused melanocortin agonist — the pigment of MT-II with far less nausea or erections.
Typical dose
500 mcg
Daily during the 10-14 day loading phase, then 1-2x weekly for maintenance
Range
250–1000
mcg
Half-life
1 h
see Dosing
Evidence
Human trials
Subcutaneous
What it is
Melanotan I is a linear 13-amino-acid analogue of alpha-MSH, identical to the native hormone apart from a norleucine at position 4 and a D-phenylalanine at position 7, which is what gives it potency and resistance to enzymatic breakdown. As afamelanotide it is a licensed medicine — Scenesse, a 16 mg controlled-release implant approved in the EU and US for erythropoietic protoporphyria.
The practical difference from Melanotan II is not receptor selectivity — afamelanotide is a superpotent but essentially non-selective agonist across MC1R, MC3R, MC4R and MC5R — it is pharmacokinetics. MT-I is a linear peptide that clears quickly and reaches the hypothalamus poorly, where MT-II's cyclic lactam is far more stable and centrally active, so users report little or no nausea, no spontaneous erections and no appetite suppression. The trade-off is that it takes more milligrams for the same tan and does nothing at all for libido.
The skin cancer caution carries over unchanged. Stimulating melanocytes with an unlicensed injectable while deliberately increasing UV exposure darkens existing moles and has been associated in case reports with new and changing naevi. Baseline mole mapping and annual dermatological review are the minimum sensible precautions.
How it works
MT-I is a potent agonist at MC1R on melanocytes. Binding raises cyclic AMP, upregulates tyrosinase and shifts melanin synthesis toward eumelanin, so the same UV dose produces a darker, faster tan and less erythema. In erythropoietic protoporphyria that increased eumelanin is what buys patients pain-free time in sunlight.
Its receptor profile is not actually MC1R-selective — NDP-MSH is a superpotent pan-agonist with high affinity at MC1R, MC3R, MC4R and MC5R alike. What limits the hypothalamic effects — nausea, flushing, erections, appetite loss — at tanning doses is pharmacokinetic rather than pharmacodynamic: a linear peptide that is cleared fast and penetrates the CNS poorly, where MT-II's cyclic lactam is metabolically stable and centrally active.
Dosing
MT-I is weaker per milligram than MT-II, so the same 250 mcg that would floor you on MT-II barely registers here; expect to use roughly twice the milligrams for a comparable tan.
Reconstitution calculator
Pre-loaded with Melanotan I’s vial size, water volume and typical dose. Change anything.
Typical: 500 mcg · range 250–1000
Draw to
20 u
0.2 mL · 500 mcg
Concentration
2.5 mg/mL
25 mcg per unit
Doses per vial
10
Vial lasts
10 days
Draw to 20 units on the barrel.
Once mixed
Refrigerated at 2-8°C, use within about 4 weeks. Keep it out of light; do not freeze.
2 mL into a 5 mg vial gives 2,500 mcg/mL, so 500 mcg is 20 units on a U-100 pin; the same 2 mL into a 10 mg vial gives 5,000 mcg/mL and 500 mcg becomes 10 units. If you prefer easier measurement at 250 mcg, use 5 mL in the 10 mg vial for 2,000 mcg/mL. Direct the water at the glass wall and swirl until clear rather than shaking.
Storage
Before mixing
Refrigerated at 2-8°C it is stable for years; sealed and dry it survives several weeks at room temperature.
After mixing
Refrigerated at 2-8°C, use within about 4 weeks. Keep it out of light; do not freeze.
Reported benefits
- ▪Deep tan with substantially less UV exposure than tanning unaided
- ▪Essentially none of the nausea, flushing or erections that come with MT-II
- ▪No appetite suppression, so it does not interfere with a bulk
- ▪Backed by real human trial data and a licensed medicine (Scenesse)
- ▪Reduces phototoxic pain and burning in erythropoietic protoporphyria
- ▪Tan persists for weeks after the last dose
Side effects
- ▪Darkening of existing moles, freckles and old scars
- ▪New or changing melanocytic naevi with continued use
- ▪Mild nausea or flushing in a minority, usually only on the first few doses
- ▪Injection site reactions and transient fatigue
- ▪Uneven pigmentation, particularly on the face and hands
- ▪More injections needed than MT-II to hold the tan — a potency and stability difference in practice, not a half-life one (both peptides clear in roughly an hour)
Do not use if
- ▪History of melanoma, or atypical or dysplastic naevi
- ▪Numerous or unmapped moles you have never had assessed
- ▪Significant hepatic impairment, which is a labelled contraindication for the approved implant
- ▪Pregnancy or breastfeeding
- ▪Immunosuppression, including transplant recipients
Evidence level — Human trials
Controlled human clinical data exists.
Approved as Scenesse (afamelanotide) implant for erythropoietic protoporphyria in the US and EU; the injectable vialled form sold to the peptide market is not a licensed product.
Melanotan I FAQ
Why choose MT-I over MT-II?+
If you only want the tan, MT-I gives it without the nausea, unwanted erections and appetite loss that come with MT-II's central MC4R activity. The cost is more injections, more milligrams for the same result, and no libido effect at all.
Do I need UV exposure?+
Yes. MT-I primes the melanocytes but UV is what actually triggers pigment output, so dosing without any sun or bed exposure produces very little. Short, controlled exposures during the loading phase are the standard approach — you can still burn on day one.
How does the vialled peptide compare with the Scenesse implant?+
Same molecule, completely different delivery. The implant is given every two months, but it does not trickle out over that whole window — most of the 16 mg is released within the first 48 hours, over 90% by day 5, plasma levels are below the limit of quantitation by about day 10, and the polymer itself is absorbed by the body over 50-60 days. That release phase is what gives the apparent half-life near 15 hours, whereas injected free peptide clears in a couple of hours and has to be redosed daily during loading. Blood levels from injections are far spikier than the licensed product's.
Will it help with libido like PT-141?+
No. Not because it misses MC4R — afamelanotide binds the central receptors about as well as MT-II does — but because as a linear peptide it is cleared quickly and reaches the hypothalamus poorly, so in practice it is a tanning compound only. If libido is the goal, PT-141 is the compound with the data behind it.
Is the mole risk lower than with MT-II?+
There is no evidence it is. Both work by stimulating melanocytes and both have case reports of darkening moles and eruptive naevi, so the same precautions apply: photograph and map your moles before starting, and have a dermatologist review anything that changes.
References
- 1.Afamelanotide for Erythropoietic Protoporphyria — The New England Journal of Medicine (2015) PMID 26132941
- 2.Skin pigmentation and pharmacokinetics of melanotan-I in humans — Biopharmaceutics & Drug Disposition (1997) PMID 9113347
- 3.Afamelanotide: A Review in Erythropoietic Protoporphyria — American Journal of Clinical Dermatology (2016) PMID 26979527
- 4.Eruptive melanocytic naevi following melanotan injection — The British Journal of Dermatology (2009) PMID 19575725
More sexual health & melanocortin
Melanotan II
Non-selective melanocortin agonist for deep tanning, with libido and nausea along for the ride.
250 mcg · Daily during the loading phase, then 1-2x weekly for maintenance
PT-141
Melanocortin agonist that works on desire in the brain rather than blood flow in the penis.
1 mg · As needed, no more than once in 24 hours and no more than 8 doses per month