Objective: 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.
Patients and methods: 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.
Results: 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.
Conclusion: The combination of VIP and PM at the dose used is a safe and effective means of treating male ED of primarily nonpsychogenic aetiology.