K4 Elite
K4 Elite
Melanotan II is a cyclic alpha-MSH analogue studied at the University of Arizona in the 1990s in a pilot phase I tanning study (3 men) and in three small double-blind, placebo-controlled crossover studies of penile erection in men with erectile dysfunction (10-20 men each), all using subcutaneous doses of 0.01-0.03 mg/kg. Development was abandoned in favour of bremelanotide. It has no marketing approval anywhere; the US FDA has treated it as an unapproved new drug since 2007 and Australia's TGA warns against its use. Published case reports link unlicensed MT-II use to melanoma, though causality is not established.
Each row records what a published study did: who it enrolled, the regimen it administered to those subjects, and what it reported. These are historical study descriptions, not protocols to follow.
| Study | Population | Regimen as reported | Primary findings |
|---|---|---|---|
| Dorr et al., Life Sci 1996 (pilot phase I, single-blind, alternating-day placebo-controlled) | 3 healthy male volunteers | Subjects received subcutaneous MT-II or saline on alternating weekdays for 2 weeks, starting at 0.01 mg/kg and escalating in 0.005 mg/kg increments to 0.025-0.03 mg/kg. | Two of three subjects showed increased facial, upper-body and buttock pigmentation one week after dosing ended; 0.03 mg/kg produced grade II somnolence/fatigue in one of two subjects, mild nausea occurred at most doses, and a stretching-yawning complex correlated with spontaneous penile erections lasting intermittently 1-5 hours after dosing. |
| Wessells et al., J Urol 1998 (double-blind, placebo-controlled crossover) | 10 men with psychogenic erectile dysfunction | Men received subcutaneous MT-II 0.025 mg/kg or vehicle placebo with 6-hour real-time RigiScan monitoring. | Clinically apparent erections developed in 8 of 10 men; mean duration of tip rigidity >80% was 38.0 minutes with MT-II versus 3.0 minutes with placebo (p=0.0045); nausea, stretching/yawning and decreased appetite were more frequent with MT-II but none required treatment. |
| Wessells et al., Urology 2000 (double-blind, placebo-controlled crossover) | 10 men with erectile dysfunction and organic risk factors | MT-II 0.025 mg/kg and vehicle were each administered twice by subcutaneous injection, with 6-hour RigiScan monitoring and questionnaires. | Subjectively reported erections followed 12 of 19 MT-II injections versus 1 of 21 placebo doses; mean tip rigidity >80% lasted 45.3 vs 1.9 minutes (p=0.047); 4 of 19 MT-II injections were associated with severe nausea. |
| Wessells et al., Int J Impot Res 2000 (pooled double-blind crossover experience) | 20 men with psychogenic or organic erectile dysfunction | Men received subcutaneous MT-II (0.025 mg/kg in the reported dose analysis) or placebo in a double-blind crossover design with 6-hour RigiScan monitoring. | MT-II led to penile erection in 17 of 20 men without sexual stimulation (mean 41 minutes tip rigidity >80%); increased sexual desire was reported after 13/19 MT-II doses vs 4/21 placebo; at 0.025 mg/kg, 12.9% of subjects had severe nausea. |
Effects recorded in the cited reports. Frequencies are those the source reported, in the population that source studied.
| Effect | Frequency / context | Source |
|---|---|---|
| Nausea | Mild nausea at most dose levels in the phase I pilot (Dorr 1996); severe nausea after 4 of 19 injections at 0.025 mg/kg (Wessells 2000, Urology) and in 12.9% of subjects at 0.025 mg/kg (Wessells 2000, IJIR). | Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II ↗ |
| Stretching and yawning complex | Reported at most MT-II doses and correlated with erection onset (Dorr 1996); more frequent than placebo in ED crossover studies (Wessells 1998, 2000). | Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study ↗ |
| Spontaneous penile erections | Intermittent for 1-5 hours after dosing in healthy volunteers (Dorr 1996); erections without sexual stimulation in 17 of 20 ED patients (Wessells 2000). | Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study ↗ |
| Somnolence and fatigue | Grade II (WHO) in 1 of 2 subjects at 0.03 mg/kg (Dorr 1996); this was the dose-limiting finding. | Evaluation of melanotan-II, a superpotent cyclic melanotropic peptide in a pilot phase-I clinical study ↗ |
| Decreased appetite | Reported more often after MT-II than placebo in 10 men with psychogenic ED (Wessells 1998). | Synthetic melanotropic peptide initiates erections in men with psychogenic erectile dysfunction ↗ |
| Skin darkening, new/changed naevi and melanoma (case reports) | Cutaneous melanoma in a 20-year-old woman after a 3-4-week course of self-injected MT-II with sunbed use (Hjuler & Lorentzen 2014); melanoma in situ (Ong & Bowling 2012); oral mucosal melanoma after MT-II nasal spray (Alsabbagh 2025). These are single cases and do not establish causation. | Melanoma associated with the use of melanotan-II ↗ |
| Regulator-listed adverse effects | The Australian TGA lists headache, nausea, vomiting, loss of appetite and facial redness as common, and for melanotan-II cites reports of increased moles and freckles, kidney dysfunction and swelling of the brain (frequencies not given). | Don't risk using tanning products containing melanotan — Therapeutic Goods Administration (Australia), 24 January 2025 ↗ |
No interactions with a verifiable citation have been indexed for this compound.
Exclusions and label contraindications recorded in the cited sources.