Melanotan II side effects and measured results
The human reports of Melanotan II side effects in these records are case reports: low-flow priapism after injection, and a renal infarction that the authors attributed to Melanotan II. In animal studies the measured results were penile erection and yawning in rats and lower body fat in obese rodents.
The measured results for Melanotan II come from animal and cell studies, not from people. In awake male rats, MT-II given into the brain or spinal fluid produced dose-dependent penile erections, and the melanocortin blocker SHU-9119 stopped them. Yawning followed brain and intravenous dosing, but not spinal dosing.
In diet-induced obese mice, MT-II reduced body weight and both visceral and subcutaneous fat, and the same pattern held in obese rats. In a 28-day rat study using osmotic minipumps, final body fat depended on the MT-II dose, whatever the rats' starting fat level. In zebrafish on a short high-fat diet, MT-II brought memory, anxiety-like behaviour and exploration back to control levels.
The human data are harm reports, not measured outcomes. One case describes low-flow priapism after abdominal subcutaneous injection, with erectile function not recovered at 4 weeks. Another describes a renal infarction most likely attributed to Melanotan II, and cites earlier reports of rhabdomyolysis and renal failure. A study of 205 forum users raised risks to pigmented skin lesions, infection, contaminated products, polypharmacy and sunbed use.
Searches for 'melanotan 2 before and after' are usually after tanning photos. None of these records measured pigmentation in people, and none has before-and-after data on human skin. The results reported here are the ones the studies measured.
Adverse events reported
| Event | As reported | Source |
|---|---|---|
| Low-flow priapism | Single case after abdominal subcutaneous injection of melanotan; managed with aspiration, irrigation and phenylephrine; erectile function not recovered at 4 weeks | Dreyer BA et al. |
| Renal infarction | Single case, most likely attributed to Melanotan II | Peters B et al. |
| Rhabdomyolysis and renal failure | Described previously in the literature, as reviewed in the same report | Peters B et al. |
| Risks raised by forum study | Pigmented skin lesions, infectious disease transmission, contaminated products, polypharmacy and sunbed exposure (205 forum participants) | Gilhooley E et al. |
| Yawning (rat) | Seen after i.c.v. and i.v. MT-II, not after intrathecal dosing | Wessells H et al. |
Outcomes measured
| Outcome | Result as reported | Source |
|---|---|---|
| Penile erection (rat) | Dose-dependent; optimal response at 1 microgram i.c.v. and intrathecal; blocked by SHU-9119 | Wessells H et al. |
| Intracorporal pressure (rat) | No increase with intracavernosal MT-II, and no boost to nerve-stimulated erections | Wessells H et al. |
| Body weight and fat (obese mice and rats) | Weight and body fat fell, in both visceral and subcutaneous fat; low-fat fed mice kept their weight | Strader AD et al. |
| Body fat (obese rats, 28 days) | Final body fat set by MT-II dose, lower than vehicle, whatever the starting fat level | Seeley RJ et al. |
| Memory and anxiety-like behaviour (zebrafish) | High-fat diet changes reversed to control levels | Wekwejt P et al. |
| Receptor potency (human MC3/MC4/MC5, in vitro) | Phe and Trp needed for activity; Arg to Ala cut potency about 100-fold | Bednarek MA et al. |
What the studies don't show
No controlled human trial in these records measured Melanotan II side effects or results, so there are no event rates. The priapism and kidney reports are single cases and cannot show how common these events are. The pigmentation effect is described in the abstracts, but none of these records measured it in people.