What is Melanotan II?
Melanotan II (MTII) is a synthetic cyclic analog of alpha-melanocyte-stimulating hormone (α-MSH). It was developed at the University of Arizona in the 1980s as part of a program to create a “safe tanning agent” that would reduce sun damage by activating melanogenesis without requiring UV exposure.
During clinical trials, researchers discovered it also produced spontaneous erections in male participants, which led to the parallel development of PT-141 (bremelanotide) — an analog optimized for sexual effects without the tanning component.
Mechanism: multi-receptor melanocortin activation
Unlike PT-141 (selective for MC3R and MC4R), MTII activates all subtypes of the melanocortin receptor:
| Receptor | Location | MTII Effect |
|---|---|---|
| MC1R | Melanocytes (skin, hair follicle) | Tanning, eumelanin production |
| MC2R | Adrenal gland | Minimal (low affinity) |
| MC3R | Hypothalamus | Appetite reduction |
| MC4R | Central nervous system | Libido, sexual function |
| MC5R | Exocrine glands | Minor effects |
This multiple activation is why MTII has broader effects (and more adverse effects) than PT-141.
Main effects
Melanogenesis (tanning):
- Activates MC1R in melanocytes, stimulating eumelanin (dark pigment) production.
- Tanning can develop even with minimal UV exposure.
- Effect is more pronounced in individuals with lighter skin phototypes (I-III).
Sexual function:
- Produces spontaneous erections in men (in trials, 80% of participants reported spontaneous erectile activity).
- Increases libido in men and women.
- More potent than PT-141 for sexual effects, but with more adverse effects.
Appetite reduction:
- Activates hypothalamic MC3R, reducing caloric intake in animal models.
- The anorexigenic effect is documented in clinical trials.
Adverse effects profile (important)
MTII has a broader adverse effect profile than PT-141 due to its non-selective activation:
- Nausea (most frequent): 50–80% of users.
- Intense facial flushing.
- Fatigue and lethargy post-injection.
- Hyperpigmentation of existing moles and freckles — warning signal: some reports associate prolonged use with changes in nevi requiring dermatological review.
- Priapism (prolonged erections): reported in cases of excessive dosing.
- Transient hypertension.
The FDA has issued warning letters about the importation of Melanotan II due to concerns about contamination of unregulated products and the risk of nevi changes.
Critical dermatological consideration
Anyone with a history of melanoma, multiple atypical nevi, or high familial risk of melanoma should completely avoid products that activate MC1R, including MTII.
Higher risk profile than PT-141. For research use only. Not recommended for use without medical supervision. Dermatological review required before and during any use.
Reported protocol (research reference)
| Vial sizes | 10 mg |
|---|---|
| Reported dose | Reported research use: 0.25–1 mg subcutaneous per day during a loading period, then maintenance doses of 0.5–1 mg before sun exposure or sexual activity. Reference values only. |
| Half-life | Approximately 30 minutes to several hours depending on the variant. |
| FDA status | Not FDA approved |