Objectives: To assess the safety, erectogenic properties, and effect on sexual desire of Melanotan II, a synthetic melanotropic initiator of erection, in men with erectile dysfunction and organic risk factors.
Methods: Ten subjects were enrolled in a double-blind, placebo-controlled, crossover study. Melanotan II (0.025 mg/kg) and vehicle were each administered twice by subcutaneous injection; real-time RigiScan monitoring and a visual analog were used to quantify the erections during a 6-hour period. The level of sexual desire and side effects were recorded with a questionnaire.
Results: Melanotan II initiated subjectively reported erections in 12 of 19 injections versus only 1 of 21 doses of placebo. The mean rigidity score of the responders was 6.9 on a scale of 0 to 10. The mean duration of tip rigidity greater than 80% was 45.3 minutes with Melanotan II versus 1.9 for placebo (P = 0.047). The level of sexual desire after injection was significantly higher after Melanotan II administration than after placebo. Nausea and stretching/yawning occurred more frequently with Melanotan II, and 4 of 19 injections were associated with severe nausea.
Conclusions: The erectogenic properties of Melanotan II are not limited to cases of psychogenic erectile dysfunction; men with a variety of organic risk factors developed penile erections. The finding of increased sexual desire warrants further investigation of centrally acting agents on disorders of sexual desire.