PMID-11035391 – Melanotan II Penile Erection and Sexual Motivation
Wessells H, Levine N, Hadley ME, Dorr R, Hruby VJ. "Melanocortin receptor agonists, penile erection, and sexual motivation: human studies with Melanotan II," Int J Impot Res, 2000;12(Suppl 4):S74-S79.
Quick Reference
| Property | Value |
|---|---|
| PMID | 11035391 |
| DOI | 10.1038/sj.ijir.3900582 |
| Year | 2000 |
| Journal | International Journal of Impotence Research |
| Study Type | RCT |
| Evidence Level | II |
| Sample | n=20 men (normal erectile function and erectile dysfunction) |
| Peptide(s) Studied | Melanotan II |
Key Findings
- Expanded follow-up to the seminal 1998 MT-II study with 20 men (both normal and ED subjects)
- 17 out of 20 men (85%) achieved erections without sexual stimulation after subcutaneous MT-II
- Sexual desire/motivation increased in 68% of MT-II-treated subjects vs 19% with placebo
- Confirmed dual effect: both peripheral erectogenic response and central sexual desire enhancement
- Demonstrates that MC4R agonism simultaneously drives genital arousal and psychological motivation
- Distinguishes melanocortin mechanism from PDE5 inhibitors, which only address peripheral hemodynamics
- Nausea and yawning remained the most common side effects
Study Design
Randomized, double-blind, placebo-controlled study in 20 men with varying degrees of erectile function. Subcutaneous Melanotan II (0.025 mg/kg) or placebo administered. Penile responses monitored by RigiScan. Self-reported sexual desire and motivation assessed via questionnaires.
Limitations
- Small sample size (n=20)
- Mixed population of normal and ED subjects complicates interpretation
- Single-dose design
- Self-report measures of desire are subjective
- Published in a supplement issue; may have received less rigorous peer review
Clinical Relevance
This study is important because it demonstrates that Melanotan II affects both the physiological (erection) and psychological (desire/motivation) components of sexual response. The 68% vs 19% difference in desire enhancement distinguishes melanocortin agonists from PDE5 inhibitors, which improve erection mechanics but do not increase desire. This dual mechanism is the pharmacological rationale for using MT-II or PT-141 in patients with combined desire and arousal dysfunction, and for the eventual development of bremelanotide for HSDD.
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#research #RCT #evidence-level-II