Treating men with predominantly nonpsychogenic erectile dysfunction with intracavernosal vasoactive intestinal polypeptide and phentolamine mesylate in a novel auto-injector system: a multicentre double-blind placebo-controlled study.

Abstract

To study the effect of intracorporeal injection (IC) of vasoactive intestinal polypeptide (VIP) and phentolamine mesylate (PM) on men with erectile dysfunction (ED) of nonpsychogenic aetiology. The study comprised 236 men with primarily nonpsychogenic ED attending sexual dysfunction clinics at eight institutions. In an initial dose-assessment phase, the men were given IC injections of 25 micrograms VIP combined with PM 1.0 mg (VIP/P-1) or 2.0 mg (VIP/P-2) in a prefilled, single-use auto-injector. The main aetiologies of ED were arteriogenic (38), diabetes mellitus (DM) (39), neurogenic (35), mixed (90), and venous leakage (30). In a placebo-controlled phase, 171 patients were subsequently treated and self-administered up to 12 injections over a 6-month interval. In the dose-assessment phase there was an overall response rate of 82%, with responses by aetiology as follows: arteriogenic (82%), DM (85%), neurogenic (86%), mixed (80%), and venous leakage (77%). In a subgroup of 159 patients who withdrew from previous IC therapies for ED, 64% responded with an erection suitable for intercourse. Of the 171 patients treated in the placebo-controlled phase, 75% responded to VIP/P-1 and 12% to placebo (P<0.001); 66% responded to VIP/P-2 and 18% to placebo (P<0. 001), with a median duration of erection of 56 min. The principal adverse event was transient facial flushing accompanying 40% of 1711 injections. There was no pain after injection and one episode of priapism (0.06%); only seven patients withdrew because of adverse events. Over 88% and 92% of patients were satisfied with the drug and auto-injector, respectively. More than 85% of patients and 77% of partners reported an improved quality of life. The combination of VIP and PM at the dose used is a safe and effective means of treating male ED of primarily nonpsychogenic aetiology.