Buckling of cylinders may cause prolonged penile pain after prosthesis implantation: case control study using magnetic resonance imaging of penis

Abstract

Editorial comments: Episodes of penile erection, and the stretching and yawning syndrome can be induced in experimental animals by CNS administration of adrenocorticotropin and alpha-melanocyte-stimulating hormone. Prior studies have suggested that melanotropic peptides act downstream to the actions of dopamine and oxytocin. The authors evaluated the erectogenic properties of Melanotan-II, cyclic alpha-melanocyte-stimulating hormone analogue. A group of ten men with no known organic cause of their erectile dysfunction were entered into the study, and the effects of Melanotan-II (given subcutaneously in the abdomen) were compared to placebo using real-time Rigiscan monitoring over a six-hour period. The authors reported a statistically significant greater number of erectile events, duration of erectile activity, degree of rigidity and tumescence activity units in the drug group versus the placebo. The drug had no effects on sexual desire. The side-effect profile was also higher in the Melanotan-II group, including stretching and yawning, nausea, decreased appetite and changes in skin pigmentation. This double-blind, crossover study is very sig-ni®cant in that it represents the ®rst placebocontrolled investigation documenting the positive erectogenic effects of an alpha-MSH analogue in humans. Interestingly, the activity and toxicity of Melanotan-II are similar to another centrally-acting erectogenic agent, apomorphine, which also acts on the dopaminergic system. The side-effect pro®le of Melanotan-II was signi®cant and may represent a limiting factor in its usefulness for the treatment of erectile dysfunction. Further studies in larger groups of individuals, including men and women, possibly utilizing different routes of administration may help us to better understand the activity of these peptides and help de®ne their role in the management of sexual dysfunction.